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Home , Amherstburg Formation, Antrim Shale, Bayport Limestone, Bedford Shale, Bell Shale, Berea Sandstone

Report of Investigation 19

Michigan Department of Environmental Quality Geological and Land Management Division

Stratigraphic Cross-Sections of the Basin - RI 19 - page 1 of 36 Stratigraphic Cross-Sections of the - RI 19 - page 2 of 36

Preface PREFACE ...... 3 STRATIGRAPHIC CROSS-SECTIONS OF THE MICHIGAN BASIN..4 In July 1975 a new unit, the Geology and Minerals Research Unit, was created in the Michigan Geological Survey Abstract...... 4 Division. The purpose of the unit is to investigate the INTRODUCTION...... 4 geology and the resource potential of the State and provide a GEOLOGIC SETTING ...... 5 data base for more detailed geological endeavors. STRATIGRAPHIC CROSS-SECTIONS ...... 5 Pertinent to these objectives, unit personnel determined that geophysical log cross-sections or correlation sections would STRATIGRAPHY AND CORRELATION ...... 6 be useful in delineating the formations in the subsurface of SYSTEM ...... 6 the Southern Peninsula in greater detail. The 15 cross- SYSTEM ...... 6 sections presented in this report cover the entire stratigraphic sequence present in the subsurface, from the SYSTEM ...... 7 Jurassic through the . They depict correlations, Bayport ...... 7 based principally on gamma ray logs, of the recognizable Michigan Formation ...... 8 groups, formations, and members in the basin, as well as Marshall ...... 9 other correlatable units or beds. The information thus Coldwater ...... 9 provided by the sections will be very helpful to ...... 10 governmental agencies, industry, university people and ...... 10 ...... 11 private citizens for an understanding of the geology of the subsurface of Michigan. It will also provide a data base for SYSTEM ...... 11 more detailed geologic study and essential information for ...... 12 more effective decisions in land use planning. ...... 12 ...... 13 The writer expresses gratitude to Garland D. Ells, Michigan ...... 14 Geological Survey, James H. Fisher, Michigan State ...... 15 University, and Glenn C. Sleight, McClure Oil Company, for ...... 15 their critical review and useful suggestions in correlating the ...... 16 many geologic formations found in the Michigan Basin. I ...... 17 am also grateful to Beverly L. Champion for editing the text ...... 18 and Gregory A. Wilson and Darrel Hodge for preparation of SYSTEM ...... 18 the plates. A special thanks goes to Robert C. Reed, who Bass Islands Group ...... 18 reviewed the text and provided many helpful suggestions in Salina Group...... 19 the preparation of this report. The writer also thanks Lois Niagara Group ...... 22 A. Padgett for rough-draft typing and Lois J. DeClaire for ...... 23 final-typing of the manuscript. ...... 23 SYSTEM ...... 23 Richard T. Lilienthal, Geology and Minerals Research Unit, Cincinnatian Series...... 24 Geological Survey Division ...... 24 Trenton Group ...... 25 ...... 25 This document is based on a scanned copy of the text of St. Peter Sandstone...... 26 Report of Investigation 19, Stratigraphic Cross-Sections of Prairie du Chien Group ...... 26 the Michigan Basin. Errors and omissions are unintended. SYSTEM ...... 26 Please report any oversights to Steven E. Wilson via email [email protected]. PRECAMBRIAN ...... 28 LITERATURE CITED...... 28 ILLUSTRATIONS ...... 31

APPENDIX 1 – WELL RECORDS USED TO CREATE CROSS- SECTIONS...... 34

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 3 of 36 Introduction Stratigraphic Cross-Sections of the The present decade has been witness to the development of Michigan Basin an intensified national concern for the wise and conservative use of our nonrenewable resources. It is also imperative that wise land-use decisions be made in any area where mineral Abstract or energy resource potential is present. To help achieve The strata of the Michigan Basin, encompassing a span of these goals, many kinds of data are needed. One type of geologic time from the Cenozoic Era into the Precambrian, data base deals with geologic information pertaining to the have been correlated in a series of cross-sections, using rock formations of Michigan's Southern Peninsula. Many gamma ray logs from approximately 100 wells drilled in new wells have been drilled in this region during the past Michigan. Fifteen cross-sections have been constructed. All decade. Because these new wells add to the geologic of the sections emanate in radiating fashion from the knowledge of Michigan, they are important in the search for deepest well drilled in the State, the McClure Oil Company - oil and gas resources, for salt and brines, and other uses. To Sparks, Eckelbarger, Whightsil No. 1-8 in Gratiot County, better delineate the stratigraphy of the rock formations in which attained a total depth of 17,466 feet. Each of the the subsurface of the Southern Peninsula and thus enhance fifteen cross-sections is composed of six or seven separate the geologic data base, a new series of cross-sections based sections, showing the entire stratigraphic sequence present on geophysical logs is presented. Fisher et al. (1969) in the wells in that particular cross-section. In conjunction constructed two cross-sections of the Michigan Basin using with the gamma ray logs depicted in the sections, other geophysical logs, and they were helpful in the preparation of geophysical logs are shown in order to demonstrate porosity, this report. density, conductivity and of the strata in various A stratigraphic cross-section or correlation section is one of parts of the basin. The terminology applied to the rock units the geologist's tools for defining and depicting the is essentially that which is used in Michigan's subsurface subsurface geology of a specific area. A series of such investigations. sections, properly constructed, will show the entire Some of the special characteristics of each formation are stratigraphic sequence as well as particular salient aspects of discussed in the text. Among these are the lithology, some the formations in various portions of the area. The cross- depositional history and the resource potential of the sections can also be used as a base from which further formation. studies can proceed. The discussion and sections of the subsurface of the Southern Peninsula are intended to show During the process of researching the rock strata of various features which may be useful in future studies. Michigan from the geophysical logs, several distinctive horizons were noted in some of the formations, which were In order to show the geology in sufficient detail, 15 separate present over a wide enough geographic area to aid in cross-sections crisscrossing the Southern Peninsula were correlating the log curves. Such horizons were especially constructed (see Plate l). Approximately 100 wells are apparent in the Traverse Group, the Detroit River Group, shown in these cross-sections, and they are listed in the Cincinnatian Series and the Black River Group. These Appendix I. The focal point from which the cross-sections horizons are useful in defining changes in the radioactivity emanate in radiating fashion is located in Section 8, T10N, of the rock and, hence, fades changes. R2W, North Star Township, Gratiot County. This key well, the deepest well drilled in Michigan, is the McClure Oil Porosity zones are abundant in several formations of Company - Sparks, Eckelbarger, Whightsil No. 1-8. This oil Devonian age, particularly the Traverse Limestone, the and gas test penetrated a portion of remnant Mesozoic Dundee Limestone and the Lucas Formation. These zones Jurassic rock and the entire sequence of Paleozoic rocks in can be utilized for defining potential hydrocarbon reservoirs, the basin. The well, therefore, was an excellent point from lost circulation zones, water zones and potential liquid waste which to anchor the cross-sections. These sections are disposal reservoirs. composed of radiation and electric logs. Gamma ray logs One of the principal intents of this investigation is to are the tools most useful in correlating formations and units provide a more complete picture of the subsurface geology in this area and they were used extensively in this study. In of the Southern Peninsula of Michigan for industry conjunction with the gamma ray logs, other logs from personnel, government agencies, educators and the general various parts of the basin are portrayed to demonstrate the public. These cross-sections can be used as reference porosity, density, conductivity, and lithology of the strata in material or guides from which more explicit and detailed a number of different localities. research on the geology of Michigan can be done. They can The purpose of this investigation is to give industry, also serve as a data base for future development planning or government and university personnel, and the private land use policy development in Michigan. citizenry a more complete picture of the subsurface geology

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 4 of 36 of the Southern Peninsula. These cross-sections can be used Much of the Michigan Basin is covered by a veneer of glacial as a data base for many purposes: exploring for oil and gas; drift. In some areas in the Southern Peninsula the rocks are delineating porosity or lost circulation zones; determining exposed at the surface, while in other areas over a thousand brine disposal or other waste disposal possibilities; providing feet of drift cover the bedrock. more information for casing points; showing more fully on a The strata which are present in Michigan range from Jurassic regional basis how to choose formation tops more age to Pennsylvanian, , Devonian, Silurian, consistently; and planning future developments in the State. Ordovician, and Cambrian (see Chart l). All of these This report is not intended for correlating the surface systems are not present over the entire area; some have been formations with their subsurface counterparts; but it may be removed by pre- erosion. useful as a base for future studies. Formation and group names in this report are those normally used in Michigan's Rocks of Jurassic age are uppermost in the basin and are subsurface investigations. located only in the central and west central portions of the Southern Peninsula (see Figure l). The next lower sequence Along with the cross-sections constructed for this of strata encountered is Pennsylvanian in age and is found in investigation are discussions of the characteristics of the central and south central portion of the State. The individual formations. The of the formations are thickness of Pennsylvanian rocks ranges from 0 to 765 feet not the same everywhere in the basin because of facies and the System is first encountered at depths from 0 to 600 changes, and some of these variations are analyzed. Other feet. The Mississippian System underlies the Pennsylvanian. points covered in the discussion are difficulties involved in It ranges from 0 to 1700 feet thick and the top of the System determining some formation limits, and controversies occurs at depths from 0 to 1100 feet. Rocks of Devonian encompassing correlations of some formations. age, below the Mississippian, underlie the entire Southern Some of the controversial correlations reviewed in the text Peninsula of Michigan except for the extreme southeastern involve the Michigan Formation and , corner. Devonian rocks range from 0 to 3600 feet in Ellsworth Shale and Antrim Shale, and the Dundee thickness and are first found at depths of 0 to 2600 feet. Limestone and Lucas Formation. Silurian rocks which underlie the Devonian, subcrop and in the extreme southeastern corner of Michigan, as well as in the eastern portion of the Northern Peninsula. Geologic Setting The top of these strata can be found at depths from 0 to 5300 feet and may be as thick as 4200 feet. The Ordovician The Michigan Basin is a relatively shallow intracratonic System is the next rock sequence encountered. These rocks structure which includes all of the Southern Peninsula, part are found beneath the entire Southern Peninsula but do not of the Northern Peninsula and parts of , Illinois, outcrop in Lower Michigan. They do outcrop, however, in , , and . It is bounded on the north by several localities in the Northern Peninsula. They are first the ; on the east and southeast by the encountered at depths from 1250 to 9000 feet in the Algonquin and Findlay arches; on the southwest by the Southern Peninsula and may be as thick as 2500 feet. The ; and on the west and northwest by the oldest Paleozoic rocks encountered are Cambrian in age. Wisconsin arch and Wisconsin Dome. The center of the These strata are sparsely drilled in the State and therefore basin is generally presumed to be at or near the region knowledge of the subsurface Cambrian rocks is very limited. surrounding (see Newcombe, 1933). Wells which have penetrated the strata, however, show that The Michigan Basin is composed predominantly of the top of the Cambrian ranges in depth from 2600 to downwarped Paleozoic and younger rocks which are 11,700 feet and that the rocks attain a thickness of 2500 feet manifested in concentric bands of and subcrops or more. beneath Pleistocene glacial drift (see Dorr and Eschman, 1971). The exterior portion, consisting of the oldest rocks, is expressed in outcrops of Cambrian along the Stratigraphic Cross-Sections shore of . The "bands" of rocks are Fifteen major cross-sections were constructed which successively younger toward the interior of the basin. traverse the Southern Peninsula of Michigan in various Jurassic age "red beds", the youngest consolidated directions from a common center (see Plate 1). Each of sediments, are encountered in the center. The Michigan these sections is broken down into smaller entities in order Basin is believed to have originated in Precambrian time to show the response of gamma ray curves and other log with a continuation of downwarping throughout Paleozoic curves in more detail. In the southern part of the State each time. On the basis of previous studies, major periods of cross-section is divided into five or six separate parts which downwarping appear to have occurred during Silurian-Salina include, in descending order: l) a section covering, where time and Devonian-Detroit River time. applicable, the Pleistocene and Jurassic, Pennsylvanian and Mississipian; 2) one showing the Lower Mississippian and

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 5 of 36 Upper and Middle Devonian; 3) a section of the Middle and Jurassic System Lower Devonian and Upper Silurian; 4) a section of Middle and Lower Silurian; 5) one covering the Upper and Middle The chart "Stratigraphic Succession in Michigan" (Chart 1) Ordovician; and 6) where available, a section of the Lower shows Jurassic sediments of the Mesozoic Era as the Ordovician and Cambrian. youngest consolidated sediments encountered in the Michigan Basin. The beds are predominantly poorly In the northern part of the Southern Peninsula the strata are consolidated sands and with gypsum beds appearing separated into sections somewhat differently. The throughout the sequence. The rocks have been described as stratigraphic sequence is thicker due to increased subsidence Kimmeridgian in age and are, for the most part, red. of the basin and more deposition of evaporites and other strata. More sections were necessary to depict the entire These Jurassic strata are found in a relatively small area in sequence. The strata included in these sections are as the central to west central portion of Michigan (Figure 1). follows: 1) where applicable, the Pleistocene and Jurassic, They have been dissected and eroded extensively by glacial Pennsylvanian and Mississippian; 2) Lower Mississippian processes of the Pleistocene Epoch; as a consequence, and Upper and Middle Devonian; 3) the Middle Devonian; Jurassic sediments are not present in all of the general area, k) the Upper and Middle Silurian; 5) the Middle and Lower but may be as much as 400 feet thick where present. The Silurian; 6) the Upper and Middle Ordovician; and 7) the beds are considered to be continental elastics. They Lower Ordovician and Cambrian, where enough wells were intertongue abruptly with other types of rock in the drilled which penetrated these rocks. sequence and show the irregular bedding characteristics typical of continental deposition. It is difficult to correlate Datums selected were the Sunbury Shale, Antrim Shale, Bell these beds on the basis of electric logs, although they have Shale, C Unit, Trenton Group, and . The been identified by Shaffer (1969) on the basis of palynology. Antrim Shale was used in the southern portion of the State in constructing a part of the Devonian section. In the An attempt has been made to correlate sediments previously northern portion, however, because of the thickness of the identified as Jurassic in age in cross-section A-D, Plate 23 on evaporites, it became more practical to use the as the basis of gamma ray log characteristics as well as some a datum. lithologic descriptions of the units. Few radiation log correlations of Jurassic sediments have been conducted in Each section contains the maximum number of formation the past. Those presented here are possible correlations, correlations deemed possible. The formations are generally and also show the stratigraphic position of the separated according to electric and radiation log Kimmeridgian in these drill holes. Further study of gamma characteristics; however, samples from several wells were ray log interpretations in the red bed sequence is essential to studied in order to tie the electric log picks as closely as facilitate accurate correlations of these sediments. possible to lithologic differences. Some formations contain individual beds which can be correlated for considerable distances and these are also shown. Pennsylvanian System Rocks of Pennsylvanian age are limited in areal extent Stratigraphy and Correlation generally to the central portion of the Southern Peninsula (see Figure 1). The Pennsylvanian System in Michigan is The sedimentary rock sequence in the Southern Peninsula of composed essentially of two formations, the Michigan ranges from Jurassic "red beds," confined to the and the Saginaw. The uppermost is central portion of the basin, to Cambrian sandstones above predominantly sandstone and is basically indistinguishable the Precambrian basement. Paleozoic rocks, from youngest from the . In past studies the two to oldest, are represented by the Pennsylvanian, formations have not been separated in the subsurface on the Mississippian, Devonian, Silurian, Ordovician, and basis of geophysical logs, and they are not differentiated in Cambrian systems. Beneath these are strata of Precambrian this investigation. age, the oldest rocks in Michigan. They are composed of various granites, , and other types of igneous, It is general practice to group all Pennsylvanian strata found metamorphic and sedimentary rocks. All of the above in the Michigan Basin into the Saginaw Formation. A systems contain formations which have had or will have maximum thickness of about 765 feet of Pennsylvanian potential for mineral resource or hydrocarbon production. rocks is found in the northwestern portion of the area of These potentials as well as other pertinent matters, such as deposition. The Saginaw is generally composed of lithology, porosity, correlation problems, and other related interbedded sandstones, shales, limestone, and coal. The subjects of interest, will be discussed in the following sandstone beds vary considerably in thickness and thin or descriptions of the formations. pinch out in relatively short distances. At the base of the Saginaw is a unit called the Parma. The medium to coarse grained is generally less than 100 feet thick Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 6 of 36 but may be as much as 150 feet in some areas. The unit The interval of geologic time between the end of the appears to be lenticular in shape and cannot easily be Pennsylvanian period of deposition and Jurassic "red beds" distinguished as a separate entity in the subsurface. deposition, as well as the time between Jurassic deposition and the beginning of the Pleistocene Epoch, were significant In early Pennsylvanian time the area of deposition was a periods of erosion of strata in the Michigan Basin. An shallow basin with a series of rivers flowing into it from the is present also at the base of the east. Previous studies of the Saginaw Formation indicate that Pennsylvanian, and this is noted on the cross-sections. several cycles of deposition occurred, and many local developed. During the total time of deposition of Pennsylvanian sediments, several minor Mississippi System inundations of the sea occurred from the northwest and west. Cyclothems were deposited during Saginaw time and Thousands of wells drilled in the Michigan Basin have were separated by other beds such as the Verne Limestone, penetrated rocks of the Mississippian System. The sequence a marine deposit. Deposition of cyclothems is indicative of is thickest in the central part of the State. The strata range an unstable coastal environment in which marine from zero thickness around the edges of the Southern submergence and emergence occur. Beds, of coal are Peninsula to 1700 feet in the center of the basin. associated with the cyclothems. Thus the sedimentary Mississippian strata outcrop in several widespread areas; in conditions ranged from marsh fluvial-deltaic on the east to other areas these rocks may first be encountered 1100 feet shallow brackish marine on the northwest and west (Cohee, below the surface. Mississippian formations include, in 1951). Pennsylvanian rocks were then covered by Jurassic descending order, , Michigan Formation, red beds. Marshall Sandstone, , Sunbury Shale, Berea In the Saginaw Formation, coal beds have been found which Sandstone, and Bedford Shale. range from a few inches to 7 feet in thickness. Most of the mined coal, however, was approximately 30 inches thick Bayport Limestone (Kalliokoski, 1976). The coal beds generally are quite thin and pinch out within a distance of a few hundred feet. The Bayport Limestone, named by Lane in 1899, is the Because the sedimentary conditions fluctuated rapidly, none stratigraphically youngest Mississippian formation of the coal seams appear to be continuous over any great encountered in the Michigan Basin. It varies from 10 to area. More than 46 million tons of coal have been produced more than 100 feet thick and consists of light to dark gray in Michigan since 1835 (Cohee et al., 1950); but no coal is fossiliferous limestone and dolomite interbedded with quartz being produced at the present time. and sandstone. The formation may also contain chert in certain zones. Some individual beds are Only one field in the State has yielded oil or gas from the lenticular and are not extensive laterally. Saginaw Formation, and that was the Elba field in southeastern Gratiot County. In the Elba field, a few wells The variability in the thickness of the Bayport is due in part in Parma sandstone produced natural gas. The amount of to an erosional unconformity between it and the overlying gas present was small and all of the wells have since been Pennsylvanian rocks. In some areas the formation has been abandoned. Future prospects do not appear to be favorable completely eroded away and the Pennsylvanian lies on the for any significant production of oil or gas from any of the Michigan Formation. Hence, the Bayport can vary from 0 to Saginaw strata. slightly over 100 feet thick, but it is generally less than 100 feet. All of the cross-sections dealing with the uppermost strata of Michigan show at least some portion of the Saginaw The Bayport appears to have accumulated in a shallow sea Formation. Very little work has been done previously on into which silt and sand were being carried from both the correlation of Pennsylvanian strata based on gamma ray log northeast and west. The abrupt lateral alternation and information and very little correlation has been attempted in intertonguing of limestone, dolomite, and sandstone indicate this report. The Pennsylvanian is generally identified only rapidly shifting environments of deposition in which waves on an individual well basis using radiation logs. Some and currents had a strong effect on the type of sediments lithologic studies have been done but none have been accumulating. The Bayport contains intraformational integrated with radiation logs and the gamma ray response. conglomerates and breccias, a fact which may imply the existence of strong wave action during part of the time of The Pennsylvanian is characterized by sequences of high- deposition. and low-radioactive strata that vary in intensity and thickness from place to place. These variations are caused mainly by The Bayport appears to have some resource potential. changes in lithology from sandstone to argillaceous material. Presently, some Bayport limestone quarrying operations The individual beds in the Pennsylvanian can probably be exist and they will probably continue in the future. Galena delineated after further detailed study. has been reported in the formation in Huron County. This reported occurrence may warrant further investigation. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 7 of 36 Future possibilities for oil and gas extraction do not appear Michigan and Iosco County in eastern Michigan. In the to be promising. future other mining operations may be stimulated by increased demand for gypsum. Another correlatable zone is Correlation of the Bayport from place to place is quite the "Brown Lime" (see Plate 2). This unit is a 10- to 20-foot difficult. This is due mainly to variations in lithology, and thick brown dolomite which can be traced over much of the the fact that little detailed correlation work has been done lower part of Michigan. The top of the "Brown Lime" is using electric logs. However, an attempt has been made in used for structure contouring in areas where gas production this report to correlate the Bayport in the central basin area is obtained from the sandstone body known as the "Stray of deposition. Sandstone". This sandstone is found about 100 to 150 feet As shown in cross-sections A-B through A-H, Plates 9, 16, below the "Brown Lime" in some fields in the central part of 23, 29, 3,», 38 and 44, the thickness of the Bayport can vary the Southern Peninsula. from well to well. This is most likely due to erosion which At the base of the Michigan is the unit known as the "Stray took place during and after Bayport deposition. The Sandstone". Several theories have been proposed regarding formation is characterized by fairly low radioactivity when the depositional history of the "Stray" and its relationship to compared to some of the overlying Saginaw Formation and the Michigan Formation and Marshall Sandstone. The underlying Michigan Formation. This is due to the typical sandstone appears to be variable in thickness and areal gamma ray response generally found in and distribution; for example, it can be anywhere from 0 to 100 sandstones, which compose the bulk of the beds. The feet thick in the central basin area. It is irregular in the Bayport is difficult to correlate because of lack of subsurface, and has been compared to the shoestring sands information on its exact position in the stratigraphic of Kansas and Oklahoma. Many geologists have included sequence on gamma ray logs, and the scarcity of studies the "Stray" in the Michigan Formation in the subsurface; but defining the formation accurately in individual wells. The they have also correlated it with the Napoleon member of position of the Bayport in this study was defined from well the Marshall in southern Michigan outcrop areas. records submitted by various companies, and an attempt was then made to correlate the lithologic description with Prior to extensive drilling in the Southern Peninsula, the the gamma ray log. contact between the Michigan and Marshall was placed at the first appearance of sandstone beneath the Michigan Michigan Formation evaporites. This practice prevailed until further drilling in the central part of the basin revealed sandstone above the The Michigan Formation underlies the Bayport in the lowermost anhydrite. This sandstone, termed the "Michigan Michigan Basin. This unit, named by Winchell in 1861, is Stray", contained large quantities of gas (see Rawlins and exposed in Kent, Huron, and losco counties. It is composed Schellhardt, 1936). The boundary between the Michigan of beds of anhydrite and gypsum, gray to dark gray and and Marshall was then placed at the first carbonate greenish-gray shale, limestone, dolomite, and sandstone. The encountered below the "Stray". As drilling progressed in the formation is economically important in that a portion is basin it became clear that a close relationship existed quarried for gypsum, and gas has been produced out of a between the "Stray" and Marshall in the southwestern area sand known as the "Michigan Stray". Presently, many of distribution. Michigan Stray gas field reservoirs are being used for gas storage. Some geologists believed that the "Stray" was younger than the Marshall and represented redeposited Marshall. Still The Michigan Formation is limited to the central part of the others were of the opinion that the upper part of the basin. The perimeter of the formation is an erosional edge. Marshall was time equivalent to the "Stray". One recent The area of Michigan Formation deposition appears to have study by Moser (1963) indicates that the Marshall in the had a complex history of erosion which began with pre- southwestern part of the State is time equivalent to the Bayport uplift and continued throughout Pennsylvanian Michigan. In the central and northeastern portions of the time. Many channels were cut into and through the basin the Marshall is postulated to be older than the Michigan Formation which were subsequently filled with Michigan and separated from the "Stray" by other units. In younger sediments. this report the "Stray" is shown as a separate entity Two units in the Michigan Formation are readily correctable whenever possible. throughout much of the area of preservation. These zones Correlation of the Michigan Formation throughout the basin are known as the "Triple Gyp" and "Brown Lime". The is complicated by the erosion surface separating it from the "Triple Gyp" (see Plate 2) is a unit consisting of three overlying Pennsylvanian rocks. Cross-sections A-B, A-C, anhydrite or gypsum beds and beds of shale. It is about 30 and A-E, Plates 9, 16 and 29, show some of the problems to 40 feet thick and can be traced over much of the central involving preglacial erosion surfaces. The top of the basin area. This zone is a potential source of gypsum, since formation has been chosen on the basis of lithology as well it is presently being mined in Kent County in western as gamma ray radiation characteristics.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 8 of 36 The Michigan "Stray" varies in thickness from 0 to 100 feet quiet water. By this time an extremely arid environment or more (see Plates 23 and 38). The "Stray", where it is well existed over both the depositional area and the adjacent developed, is generally located about 100 feet below the land. Streams carried sand into the depositional area from "Brown Lime"; or it may be as close as 50 feet or less (see the Wisconsin Highland intermittently during the initial Plate 38) below the "Brown Lime" marker. The base of the stages of deposition of the Michigan Formation. Michigan is generally picked at the last large radioactive Investigators in the past had thought that the red portions of response before the clean Marshall is encountered (see Plate the Marshall could be used as stratigraphic markers. 23). Correlation is especially difficult in the southwestern However, enough data is now available from Moser (1963) portion of Michigan and the correlations presented are and other researchers to indicate that red coloring in tentative at best. The high radioactivity normally found at Marshall deposits is of little value as a stratigraphic marker the base of the Michigan "Stray" decreases in this area, from a regional point of view. It has also been shown that making correlation difficult. red coloration is not limited to lower Marshall strata. Although red sediments are more characteristic of lower Marshall Sandstone beds, they are also present in the uppermost part of the The next lower Paleozoic formation to be encountered is formation in western Michigan. The base of red sediments the Marshall Sandstone. It is composed predominantly of does not necessarily signify the base of the Marshall. sandstone and silt-stone, with some zones exhibiting red Therefore, it does not seem practical to separate the lower coloration. The Marshall, named by Alexander Winchell in Marshall Sandstone from the upper Marshall (Napoleon 1861, is exposed in Jackson, Hills-dale, and Calhoun Sandstone) on a regional basis because of the red color. counties in southern Michigan, Ottawa County in The Marshall Sandstone has not yielded significant southwestern Michigan, and Huron, Tuscola, and possibly quantities of oil or gas, although some production has Sanilac counties in eastern Michigan. accrued. Prospects for a significant increase in oil and gas According to several investigators, i.e. Monnett (1948), potential do not appear to be promising and the Marshall, Cohee (1951), and Moser (1963), Marshall time was therefore, is not considered a good exploration or drilling introduced by crustal movements in the basin and in the target. Brine is produced from Marshall deposits in Gratiot adjacent land areas. The crustal movements resulted in County and rough dimensional stone is quarried from the uplift of granitic rocks in the Wisconsin Highland area. Napoleon member in Jackson County. These rocks became an important source of sediments for The top of the Marshall in this study is picked at the base of the Michigan Basin for the first time during the the last high radioactive "kick" in the Michigan, just before a Mississippian Period. The first sediments from this area cleaner Marshall sand is encountered. This is true whether appear to be fine grained red and buff sands which were or not the "Stray" is present. An examination of Plates 9, 16 deposited on the Coldwater. and 23 reveals that this gamma ray curve can be used for In the eastern part of the State, according to Monnett correlation purposes with some degree of accuracy in most (1948), no sudden change in type of deposits occurred in areas. early Marshall time because the sediments were from the A study of the sections discloses that the thickness of the same source and manifested the same lithologic character as Marshall may vary because of the presence of the Michigan the nearshore facies of the Coldwater. A gradual rise of the "Stray". Examination of the cross-sections also shows that land surface on the east is postulated, which resulted in a the lower portion of the Marshall is slightly more radioactive westward migration of the shoreline. Throughout Marshall than the upper portion (see Plate 2). This variation in time the depositional basin was shrinking due to elevation of radioactivity, as reflected in the curves, is a useful tool for surrounding land areas. correlating the Marshall. Near the middle of Marshall time, the part of the Laurentian upland which had been the eastern source of Coldwater and Coldwater Shale lower Marshall sediments began to rise. During this time The next Mississippian formation encountered immediately medium grained and some fine-grained sands were brought below the Marshall Sandstone is the Coldwater Shale. It into the Marshall sea from the east and west. These sands consists predominantly of gray and bluish-gray shale, is were deposited over the sea floor, with the thickest micaceous in some areas, and contains lesser amounts of accumulations in low areas and the thinnest on limestone, dolomite, siltstone and sandstone. Wherever it is topographically high areas. present, it overlays the Sunbury Shale and Ellsworth Shale. According to Monnett (1948), Marshall deposition did not It was named by Lane in 1893 from exposures in the end simultaneously in all areas. The first deposits of the Coldwater River near the town of Cold-water in Branch Michigan Formation accumulated in the more placid portion County. It is also exposed at other places in Branch County of the sea while Marshall sands were being deposited in less and Hillsdale County, and along the shore of in

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 9 of 36 Huron and Sanilac counties. A red argillaceous limestone or Several units are present in the Coldwater which can be dolomite unit at the base of the formation, known as the correlated in more detail. The Coldwater "red rock" at the Coldwater "red rock", is persistent over much of the basin base of the formation is a persistent unit which can be and varies from 10 to 20 feet in thickness. traced over much of the basin. This unit generally has a lesser radioactive response than the sediments above or the On the western side of the Southern Peninsula the Sunbury Shale beneath. It thickens on the western side of Coldwater Shale contains an argillaceous dolomite zone the State, as seen on Plates 29 and 34. known as the "Coldwater Lime" or "Speckled Dolomite" (Hale, 1940 (see Plate 3,0 • This facies can be correlated Some sandstone and limestone beds in the formation could through much of western Michigan. Eastward, it grades into be correlated if more meticulous studies were performed. shale. In the eastern part of the State several sandstone beds The accomplishment of petrographic studies and more appear in the Coldwater, particularly in the upper portion. detailed correlations could help to unravel the depositional The uppermost sandstone beds make it especially difficult to history of the Coldwater. define the contact between the Marshall and Coldwater. One of the sandstone beds in the lower part of the Sunbury Shale Coldwater, the "Weir sand", actually yields some shows of gas. A few gas wells have been completed in the "Weir The Sunbury Shale, generally underlying the Coldwater in sand". An occasional show of oil is found in the limestones the Michigan Basin, extends over a large part of the of the Coldwater shale on the west side of the State. Southern Peninsula. The Sunbury was first identified in 1900 by R. C. Lane in samples from a well drilled on the campus A noticeable feature of the Coldwater is the prominent of the University of Michigan in Ann Arbor. Because it is a thinning of sediments from the center of the State to the readily recognizable unit which extends over a wide area, it is western margin (see Plates 34 and 38). While the formation a good correlatable marker bed over much of the basin. No is approximately 1,000 to 1,100 feet thick in the central and outcrops of Sunbury Shale have been found anywhere in the eastern parts of the State, it thins to about 500 to 600 feet in State. western Michigan. It also thins in a southward direction from central Michigan, but the thinning is much less than The Sunbury Shale underlies Coldwater rocks except where toward the west. it pinches out or grades into the Ellsworth Shale on the western side of the State. It is quite similar to the Devonian The westward thinning of the Coldwater seems to reflect Antrim Shale lithologically and ranges in thickness from either an overlapping of the sediments on higher structure zero in the western portion (see cross-section A-G, Plate 38) or thinning away from an eastern source. The lithology of to about 120 to 140 feet on the eastern side (see cross- the formation indicates westward convergence as opposed section A-N, Plate 76). In the eastern part of the State it to any loss of lower beds, which would be expected in an overlies the Berea sandstone, but in most of the western overlap situation; so the first possibility seems unlikely. portion it overlies the Ellsworth Shale. It appears that the Coldwater Formation thickens geometrically to the east where coarse elastics prevail in the Berea Sandstone formation. It is significant to note that the percentage of sand is highest in those areas where the Cold-water reaches The Berea Sandstone, underlying the Sun-bury, was maximum thickness. This could be interpreted to mean that identified by Rominger in 1876 in a well drilled in the in addition to being in closer proximity to the inferred Courthouse Square at Ann Arbor. The formation is source, the coarse clastic sediment distribution is related to confined to the eastern side of the State and appears to be a the subsidence of the Coldwater depocenter. The higher deltaic-type deposit. It grades into the upper Ellsworth on quartz sand content suggests that the eastern part of the the western side of the Southern Peninsula; but a small basin was a nearshore environment and the water was very amount of the Berea unit may be present in the Ellsworth in likely shallow. The percentage of elastics decreases some of the western counties. The sandy unit has, in the westward; i.e., clastic content is close to 100 percent in past, been called the "Berea" or "Berea Horizon" (Hale, eastern and central Michigan and decreases to 60 to 70 1941). The zone, where present on the western side, percent in western Michigan (Chung, 1973)- becomes a dolomite with a small amount of sand rather than being a completely sandy horizon. The Berea overlies the The correlation of the Coldwater throughout the basin is Bedford everywhere on the eastern side of Michigan and the fairly simple and straightforward. The Sunbury Shale, where contact appears to be gradational. it exists in Michigan, serves as an excellent base. The upper portion of the Coldwater is sometimes difficult to correlate The Berea Sandstone is generally separated into three in part of eastern Michigan because of the transitional nature lithologic units (Cohee and Underwood, 1940). The lower of the contact with the Marshall. The top of the Coldwater unit is light gray, fine grained, dolomitic, silty and shaly, was chosen at the first high-radioactive response below the micaceous, pyritic sandstone, cemented with silica. The Marshall Sandstone beds, as shown on Plates 23 and 76. middle unit is friable, fine grained sandstone composed of Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 10 of 36 angular quartz grains. Thin beds of shale and tightly Shale and upper part of the Antrim Shale on the western cemented sandstone are interbedded with the friable side of the State. sandstone in places. The upper unit is lithologically similar In this report the Bedford is generally confined to that to the lower unit but is less shaly and pyritic. These units, portion which is composed predominantly of gray shale. It although identifiable lithologically, cannot be separated on may contain some sandstone or siltstone beds, especially at the gamma ray logs, so they are not delineated on the cross- the transitional contact with the Berea, but it is usually sections. distinguished without much difficulty. The Bedford shows Natural gas and oil have been produced from the Berea greater radioactivity than the Berea above, as seen on Plates Sandstone in several areas in eastern Michigan. The most 71 and 77; and it is much less radioactive than the important fields which have produced oil are the Saginaw underlying Antrim. These criteria can be used to bracket the and Birch Run fields in Saginaw County, the Otisville field in Bedford for purposes of correlation. northeastern Genesee County, and the New Lothrop field in As a result of stratigraphic, paleontologic, and palynologic Shiawassee and Genesee counties. Some of the more studies of these formations by Dewitt (1970), the important gas-producing fields are Clayton, Deep River, and Mississippian-Devonian boundary in northern Ohio is North Adams fields in Arenac County and Logan field in placed in the basal 2 to 10 feet of the Bedford Shale. Ogemaw County. Other fields in the eastern part of the Whether the basal part of the Bedford Shale in the Michigan State have produced from the Berea, and wells outside of Basin is of Devonian or Mississippian age is a moot point at these fields have had shows of oil and gas. present according to Dewitt (1970). In the western portion The producing zone, located in the upper part of the of the State where the Berea and Bedford are absent, the top sandstone, is from 13 to 16 feet thick and is generally of low of the Devonian is placed near the top of the Ellsworth, permeability. Initial production from the oil wells ranged based on correlation from the eastern part of the basin. For from 5 to 185 barrels per day and from the gas wells 1 convenience, general practice is to place the Mississippian- million to 16 million cubic feet of gas per day. Devonian contact at the top of the Antrim in eastern Michigan, and at the top of the Ellsworth in western The "Berea" dolomite on the western side of the State has Michigan. also yielded hydrocarbons. Some of the fields are found in Muskegon and Oceana counties; most of them produce oil. The Berea Sandstone in eastern Michigan is easily correlated, Devonian System with some possible minor difficulties in recognizing the basal portion because of the transitional contact with the Rocks of the Devonian System are found beneath Bedford. The upper contact is easily distinguished from the Mississippian strata. Thick sections of Upper and Middle Sunbury Shale. The Berea generally includes all those Devonian rocks are present in the Michigan Basin, but portions of sandstone and shale or dolomite above the more Lower Devonian strata are essentially absent. The only consistent Bedford Shale, as shown in cross-sections A-M, rocks of Lower Devonian age which may be present, those A-N, and A-0, Plates 71, 77 and 85. of the highly eroded , are not readily identified in the subsurface. Approaching the central portion of the basin, the Berea starts losing its identifying characteristics and is not generally Devonian formations and groups identified in the distinguished from the Bedford below. The Berea gradually subsurface of the Southern Peninsula are, in descending changes to a dolomitic and shaly entity and eventually grades order, the Ellsworth Shale confined to the west side of the into the upper Elsworth on the western side of the Southern basin; Antrim Shale; ; Traverse Peninsula. In the central portion of the basin where the Limestone; Bell Shale; Dundee Limestone; Detroit River Berea and Bedford are not easily distinguished as separate Group; and Bois Blanc Formation. The Detroit River entities, the unit is generally called the Berea-Bedford (see Group is composed of the Lucas Formation, the Plates 10 and 17). Amherstburg Formation, and Sylvania Sandstone. From an economic standpoint, rocks of the Devonian Bedford Shale System are of prime importance to the people of Michigan. A major proportion of the petroleum produced through the The Bedford Shale, identified by Rominger in 1876, is years has come from rocks of Devonian age. Potential for predominantly gray. As stated previously, the Berea and future production of hydrocarbons is excellent. Many of the Bedford contact is gradational in some areas where the currently active fields are expected to continue supplying oil upper part of the Bedford may be silty and sandy. It is and gas, and prospects for new discoveries remain good. confined to the eastern part of the State. Several of the The significance of Devonian rocks from an economic cross-sections show that both the Berea Sandstone and the standpoint will be reviewed in more detail in sections dealing Bedford Shale grade into or interfinger with the Ellsworth with the individual formations.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 11 of 36 Ellsworth Shale In some areas of northwestern Michigan the basal portion of the Ellsworth shows increased radioactivity (see Plate 24, the The Ellsworth Shale is the uppermost Devonian formation Henry No. 1-4), and this portion has, in some cases, been encountered in Michigan. It is found, for the most part, on included in the Antrim. In this report, however, the higher the western side of the State in the same stratigraphic radioactive area is included in the Ellsworth because recent position as the Berea, Bedford and the upper portion of the Michigan Geological Survey studies have indicated that it Antrim on the east side. It was first described by correlates with some of the lower Ellsworth beds (Ells, Newcombe in 1932 in cuttings from a well drilled for oil at 1979). Muskegon. Ellsworth Shale is exposed at a few localities in Antrim and Charlevoix counties. Antrim Shale The Ellsworth is predominantly green shale in both the surface and subsurface; but some gray and greenish-gray The Antrim Shale was named by Lane in 1901 from shales occur near the contact of the Ellsworth and Antrim in exposures found in the northwestern corner of Antrim the subsurface. Ellsworth beds are quite silty in places in County. Exposures can also be seen in Charlevoix, western Michigan, particularly in the southwestern portion Cheboygan, and Alpena counties. It has a range of thickness where a considerable amount of siltstone is interbedded with from 120 feet where it is not cut by Pleistocene erosion to the greenish-gray shale. Where it is present on the western 600 feet in portions of northern Michigan. The Antrim is side of the State, the Ellsworth can range in thickness from predominantly dark gray to black and brown, hard, thin- 250 feet to as much as 700 feet. bedded, brittle, carbonaceous shale interbedded with gray shale in the lower part. Near the base of the Antrim, dark According to Bishop (1940), the depositional environment brown bituminous limestone concretions occur. They are of the Antrim, which underlies the Ellsworth, was from two to five feet in diameter and consist of a variety of characterized by a gradual increase in both temperature and calcite called anthraconite. and marcasite grains are humidity. Vegetation thrived in this climate and became associated with the anthraconite. These concretions are available eventually for deposition in the Antrim seas. unique in that they are found only in the Antrim Shale in Incorporation of the vegetation in the sediments gave the Michigan, and in Antrim equivalents elsewhere. Antrim its characteristic black or brown color. Later, a period of increased aridity, during which the greenish-gray According to Asseez (1967), the Antrim sea in Michigan was Ellsworth Shales were laid down, culminated in a withdrawal widespread and must have received a great quantity of of the sea. and erosion followed, giving rise to organic matter which resulted in deposition of the widespread oxidation of the exposed Ellsworth formation. characteristic black to brown shale. He also believes that the With the beginning of Coldwater time, southwestern Antrim was deposited in an euxinic environment, whereas Michigan was downtilted toward the northeast, and the the Ellsworth Shale accumulated in a more open sea on the minor basin in which the Ellsworth was deposited lost its western side of Michigan in alternating oxidizing and identity. From the northeast the Coldwater sea then reducing environments. The lighter colored green shale of transgressed upon the exposed Ellsworth, incorporating the Ellsworth was caused by green varieties of clay minerals, oxidized debris in the basal member of the Coldwater chiefly glauconite, as well as the abundance of ferrous ions formation. These, then, were Bishop's ideas concerning the and the scarcity of organic matter. For a more complete depositional history of the Ellsworth and the contiguous discussion of the Antrim, refer to Ells (1979). formations. The Antrim Shale may contain important hydrocarbon The correlation of the Ellsworth Shale in western Michigan resources for use in the future. This formation is currently and its transitional contact, facies relationship, or being studied in more detail by several groups in order to interfingering with the Berea, Bedford, and Antrim is shown determine its hydrocarbon potential. Some wells in Otsego on several of the cross-sections. If a line is drawn from County have produced Antrim gas for a number of years, western Charlevoix County to western Branch County, it and there may be potential for more Antrim gas in other will mark the area of transition from Berea, Bedford, and the areas of the State. upper part of the Antrim on the east to Ellsworth on the The Antrim unit has a complex geologic history and is west. This transition area (shown on cross-sections A-D somewhat complicated to correlate. As reported in the through A-I, Plates 24, 30, 35, 39, 45 and 51) is where the discussion of the Ellsworth, the upper part of the Antrim on Berea, Bedford, and upper part of the Antrim lose their the eastern side of the State interfingers with, or exhibits a specific radioactive characteristics and change to the typical facies relationship with, the Ellsworth in western Michigan. green shale radioactivity of the Ellsworth. Probably, more Therefore, delineating the true top of the Antrim can be of a facies or interbedding change between the units exist difficult in some of central and northern Michigan, as shown than is shown on the cross-sections; but for the purposes of on cross-sections A-D, A-E, and A-F, Plates 24, 30 and 35. this report, the change is shown as being rather abrupt. These sections show an abrupt change from a large Antrim section on the east to a much thinner unit on the west. A Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 12 of 36 detailed study of the Antrim has been done by Ells (1979), shales become more calcareous and the limestones purer in and should be referred to for a more complete central Michigan. In the western part of the State the full understanding of this interval. section of the Traverse Limestone is predominantly pure limestone with some beds of dolomite and argillaceous Another problem involving the Antrim is the transitional dolomitic limestones. In southwestern Michigan some nature of lower beds with the underlying Traverse Group in lithographic limestone beds are present in the lower part of certain areas of the State. In southern Michigan the contact the unit and chert is also abundant in some of the pure is, for the most part, easily recognized because the transition limestones. Reefs have been found in Alpena County zone is small and a fairly clean break occurs between the quarries and probably exist in the subsurface in other parts highly radioactive Antrim and the Traverse Group. In of the State. Observed reef buildups occur with reef heights northern Michigan, however, this transition zone is much of 30 feet and exhibiting dips of 30° to 40° on the flanks. more extensive and presents a more complicated picture. As can be seen on cross-section A-C, Plate 17, the upper part of The Bell Shale is the lowermost formation of the Traverse the Traverse Group contains some highly radioactive beds Group and is consistently shale where present. It is about which, in some previous studies, have been included in the 80 feet thick in the outcrop area in Presque Isle and Alpena Antrim. In this report the base of the Antrim has been counties and more than 100 feet thick near Saginaw Bay in chosen at the last extremely radioactive zone discernable eastern Michigan and in Manistee County in western before the general transition to less radioactive shales. Michigan. It is generally 60 to 70 feet thick in the central basin area, but thins toward the south where it eventually Traverse Group pinches out. The Traverse Group in the subsurface of the Michigan The Traverse Limestone has been a prolific producer of oil Basin is generally divided into three units. These units, in and gas in the Michigan Basin since the late 1920's. A descending order, are the Traverse Formation, Traverse number of fields in the Southern Peninsula have yielded oil Limestone, and Bell Shale at the base of the Group. It is and gas from Traverse Limestone, with the Walker field in difficult to correlate these subsurface units with the many Kent and Ottawa counties being the most prolific to date. surface formations of the Traverse. A study of the Traverse Over 17,150,000 barrels of oil had been produced in the Group directed toward correlating the surface and Walker field by the end of 1977, and about 99 percent was subsurface expressions would be most helpful. Traverse from Traverse Limestone. rocks are found at the surface in Alpena, Presque Isle, Most of the Traverse fields are located in the southwestern Cheboygan, Emmet, and Charlevoix counties in the quadrant of the State, where the Traverse is predominantly northern part of the Southern Peninsula but do not crop out carbonate. Some of these fields may be producing from in southern Michigan. The Traverse Group is variable in small bioherms in the Traverse, while in others production is thickness, with a maximum of about 875 feet near Saginaw a result of porosity pinchouts. Still other fields may be Bay and a general thickness ranging from 800 feet in the located on structural traps caused by folding, or salt collapse north to less than 100 feet in southwestern Michigan. The of the A-l, A-2, or B evaporites in the Sa1ina which has lithology is diverse in the subsurface, with many facies resulted in formation of traps in the Traverse (see Mesolella changes throughout the sequence (see Cohee, 1947). and Weaver, 1975). Porosity in Traverse Limestone The Traverse Formation, the uppermost unit of the group, reservoirs can be as much as 9 percent and ranges from is considered by many to be a transition zone between vugular to intercrystalline. Permeability is as high as 100 Antrim Shale and Traverse Limestone. The unit in the millidarcies. Though the Traverse rocks have been drilled central and western part of the State is composed of gray intensively in some parts of the basin, well density figures shale in the upper portion and gradually grades to more show large areas of poorly explored but potentially calcareous shale and argillaceous limestone near the base. productive territory yet to be drilled. The Traverse Formation in eastern Michigan is not the same The Traverse Group has been correlated in more detail than lithologically and is not easily correlatable with the central many of the other subsurface formations. It has been and western facies. It is, therefore, common practice in separated into Traverse Formation, Traverse Limestone, and subsurface stratigraphic interpretations in the eastern part of Bell Shale, which are the correlatable units. the State to combine the Traverse Formation and the Traverse Limestone. The upper portion of the Traverse Formation has been considered to be transitional between the Antrim Shale and The middle unit of the Traverse Group is the Traverse Traverse Limestone. The Traverse Formation is not well Limestone. Variation of facies is more prevalent in this unit developed in the eastern and southeastern portion of the than in the others. In eastern Michigan, the so-called State, so it is not usually described as a separate entity in Traverse Limestone is predominantly shale with the highest these areas. As seen on Plates 3, 10, 17, 24, 35, 39, 45, 51, percentage of shale content being located in the "thumb" and 57, the Traverse Formation becomes more discernible area of southeastern Michigan. Progressing westward the in a western and northern direction. The upper radioactive Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 13 of 36 portion of the Traverse Formation, which is that part above the two units in certain areas, but overall the Rogers City correlation line TF-1 (see Plate 10), can be delineated in and Dundee are not readily separable. much of western and northern Michigan. This correlation The term Dundee was first used by Lane in 1895. Dundee line is useful in determining the base of the Antrim Shale rocks underlie most of the Southern Peninsula, and are and the top of the Traverse Limestone. Within the Traverse directly beneath the glacial drift in Wayne and Monroe Limestone, six recognizable horizons, TL-1 through TL-6, counties in southeastern Michigan. They are exposed at the are delineated and traced on many of the gamma ray log surface in Sibley quarry in Wayne County and along Mason sections. These correlative horizons provide a basis for Creek in Monroe County. The greatest thickness of Dundee following facies changes in the subsurface. In addition to the rock, including the , occurs in the correlative horizons, several porosity zones in the Traverse area near Saginaw Bay where it may be as much as 475 feet Limestone are delineated in certain areas of the State, and thick. In most of western Michigan, Dundee strata are less these are correlated on many of the sections. than 100 feet thick with much of the area containing less From the top of the Traverse Limestone to the top of than 40 feet. The formation is absent in the extreme horizon TL-3, the section generally contains more carbonate southwestern portion of the State. than the section from TL-3 to the Bell Shale throughout The Dundee Limestone is predominantly buff to brownish- northeastern Michigan. An example of this is shown on gray, fine to coarsely crystalline limestone. Exceptions to Plates 3 and 10, where the lower portion contains an this occur in the extreme western and southwestern areas appreciable amount of shale and the upper portion is where the formation is entirely dolomite. In much of the composed of limestone, calcareous shale and shale. In central basin it is composed of both limestone and dolomite western and northwestern Michigan the Traverse Limestone with some anhydrite beds. Dolomite is generally found at is predominantly calcareous above horizon TL-4, whereas the base of the formation. According to Gardner (1974), the below this marker, clay content increases slightly (see Plate Dundee appears to be a biostromal shelf carbonate with 24). In southern Michigan the Traverse Limestone thins a dark fine grained offshore facies deposited in a sea great deal and the markers are very useful in correlations in transgressing from east to west. A sabkha-lagoonal facies on that part of the basin. the west records the retreat of evaporite deposition from the A series of porosity zones is present in the upper portion of Michigan Basin. the Traverse Limestone. As seen on cross-sections A-B To date, the Dundee has been the most prolific oil producer through A-J (Plates 10, 17, 24, 30, 35, 39, 45, 51 and 57) in the State. Several porous zones in the formation produce many of these porosity zones can be traced from well to well oil and gas. Lost circulation and water zones may also occur over large areas. The porosity zones furnish valuable where porosity is present. Studies have shown that these information because they point out where possible lost porous zones are lenticular and vary considerably in circulation zones or hydrocarbon-bearing zones may occur. thickness and permeability. The porosity may be either Many of the zones have been found to contain water; but indigenous or secondary and occurs in both limestones and abundant economic deposits of hydrocarbons have also dolomites of the Dundee. been found in the Traverse Limestone. One important porosity zone in the Dundee that can be The Bell Shale is the basal formation of the Traverse Group. traced over a large area is the "Reed City". This zone has As shown on the cross-sections, the Bell can be traced over produced large quantities of oil and gas. It has been a large part of the basin with some degree of accuracy. variously interpreted as part of the Dundee Limestone or Cross-sections A-G and A-l (Plates 39 and 51) in particular part of the Detroit River Group. Study still continues show that the Bell pinches out in the southern portion of concerning the "Reed City" and its age relationship with the the basin, and the contact between the Traverse Group and Dundee and Detroit River. the underlying Dundee Limestone becomes more tentative. The "Reed City" can be correlated over a large portion of Dundee Limestone the basin. A report by Landes (1951) places the zone in the uppermost part of the Lucas Formation at the top of the The next Devonian formation which is readily recognizable Detroit River Group. Where the "Reed City" is productive in the subsurface is the Dundee Limestone. The Dundee in of oil and gas, it yields non-sulfurous, sweet crude from this report combines both the Rogers City Limestone and vugular and inter-crystalline porosity in dolomite beneath an Dundee Limestone, as they are not generally distinguished in anhydrite bed. the subsurface on the basis of radioactivity logs. The differentiation into two formations by previous workers (see In this report, the "Reed City" porosity zone is placed in the Cohee and Underwood, 1945; Knapp, 1947) was based Dundee, and therefore the formation may be of greater largely on faunal succession and minor differences in expanse than the generally accepted norm, especially in lithology between the units. Minor differences in the color portions of southern Michigan. However, in tracing the as well as the lithology of part of the rock poorly distinguish Dundee from the northern part of the basin, where it is well Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 14 of 36 developed in the subsurface, to the southern two to three contact, e.g., dolomite versus limestone, color differences, tiers of counties, the correlations seem to point to a thicker and crystallinity. section in southern Michigan. In southeastern Michigan, however, correlation of the base Lucas Formation of the Dundee becomes especially difficult (see cross- The uppermost rocks of the Detroit River Group constitute sections A-K through A-0, Plates 62, 66, 71, 78 and 86). In the Lucas Formation. In the central part of the basin the the reports of several researchers, including Gardner (1974) formation consists of beds of dolomite, anhydrite, salt, and Majedi (1969), the base of the Dundee in this area has limestone, and sandstone. Some of the carbonate rocks are been placed at different horizons. It has been variously argillaceous, but shale is conspicuously absent. The Lucas chosen at: 1) gamma ray log marker DR-1 (Gardner, 197,0; varies in thickness from as little as 20 feet in Berrien County 2) below this particular marker and the good porosity zone in the southwestern corner of the State to over 1,000 feet in (Majedi, 1969); 3) above the marker and within the good the central portion, where much of the section is composed porosity (Gardner, 1974; Majedi, 1969); and 4) above the of evaporites. marker and above the good porosity (Gardner, 197,0 • The evaporites of the Lucas Formation are principally The writer has attempted to distinguish the base of the anhydrite and salt. The anhydrite is much more widespread Dundee in southeastern Michigan after correlating it in a than the salt, which is usually confined to the upper half of representative section in northern Michigan. Inspection of the evaporite sequence in the central part of the basin. the several cross-sections from the southeastern area reveals According to Gardner (1974) all of the salt appears to lie that the base of the Dundee may be in a porous-looking within the 500-foot thickness line of the Lucas, and most of interval according to neutron readings in some areas (see the salt having an aggregate thickness exceeding 400 feet is Plate 66, the Messmore No. 1) and below this zone in others confined to the deepest part of the basin in Missaukee and (see Plate 71, the Noonan No. 1-14). The writer believes, Roscommon counties, where the formation is more than however, that the base is above the high-radioactive marker 1,000 feet thick. bed, DR-1, in most cases. Anhydrite in the Lucas Formation generally increases in Previous mention has been made of several good porosity abundance basinward. Gardner (1974) has shown that in zones in the Dundee which can be traced over much of the the center of the basin anhydrite occurs above and basin. These porosity zones, as shown on several of the interstratified with salt; but the greatest volume is found in cross-sections, are critical because of their water content and the lower half of the evaporite sequence, below the salt the possibilities for lost circulation. They have also been beds. Although salt is not present away from the central significant as prolific oil producers, and the potential for the portion of the basin, anhydrite is still fairly abundant toward discovery of more oil still exists. As seen on cross-sections the rim; but the amount gradually decreases at the flanks of A-B through A-J, Plates 11, 18, 25, 30, 35, 39, 45, 51 and 57, the basin. porosity zones can be followed readily on the neutron logs. And pinchouts in porosity are significant in the search for Several oil and gas producing zones are present in the Lucas hydrocarbons. Formation. These are, in ascending order: the Richfield zone, the "sour zone", and the "Reed City" zone, if the Reed Detroit River Group City is placed in the Detroit River Group rather than in the Dundee. The Richfield generally includes all of the section The Detroit River Group, which underlies the Dundee, is that produces sweet crude below the massive anhydrite, composed of three formations in the subsurface: the Lucas which underlies the lowest Detroit River salt beds, and Formation, the Amherstburg Formation and the Sylvania above the fossiliferous black coralline limestone of the Sandstone (see Chart l). The Anderdon Formation, known Amherstburg (Hautau, 1952). Where the Richfield is best from surface exposures, is not ordinarily identified in the developed, it appears to span an interval of about 200 feet. subsurface, but is included in the uppermost beds of the The section is comprised of several dolomite beds, ranging Lucas Formation. The rocks of the Detroit River Group are from a few inches to 10 feet in thickness, separated by present over virtually all of the subsurface of the Southern anhydrite and some limestone lenses. Six of the beds have Peninsula and are variously composed of dolomite, shown oil saturation and four are considered important anhydrite, salt, dark brown to black limestone and reservoirs. Oil and gas accumulations in Richfield pools are sandstone. It is difficult to determine the contact between generally related to anticlinal structures, and most of those the Dundee and Lucas Formation in some places; but that have been found so far are associated with the larger stratigraphers generally place the contact at an anhydrite bed central basin anticlines. Richfield porosities range up to 30 which occurs within a few feet of the top of the Lucas percent, and the average porosity for total pay sections in Formation, where such an anhydrite is recognizable (see individual pools is between 14 and 17 percent. Plate 25). Where the anhydrite bed is not present, other Permeabilities range from 5 to 60 millidarcies and average 4 lithologic differences become the basis for selecting the to 6.5 for overall pay sections in individual pools. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 15 of 36 The "sour zone" produces a high-sulfur oil and gas from which, in turn, overlies the Richfield (see Plate 18, the Yake thin, low-permeability, porous dolomite and limestone strata No. l). found between thin salt and anhydrite beds through an The Richfield is the lowest portion of the Lucas, as shown interval of about 100 - 150 feet. In the central part of the on Plates 4, 11, 18 and 25. Several porosity zones located in basin where salt beds are thickest, the "sour zone" lies the Richfield can be correlated over the central and northern between a thick salt bed and an underlying anhydrite Michigan area. These porosity zones may contain valuable sequence. "Sour zone" production is generally associated hydrocarbons. In southern Michigan, the Richfield is not as with anticlinal structures in the central basin area. well developed as in northern Michigan, and cannot be The Lucas Formation has been significant in production of correlated with as much accuracy. The porosity is not as well salt and brine. Salt in the Lucas has been exploited by the developed, nor is the formation as productive of oil. brine well method in Manistee County since 1881 and in Another oil zone, not correlated in these cross-sections but Mason County since 1886. These salt-producing areas are identified on several of the sections, is the "sour zone" (see close to the western edge of deposition of the salts. The salt Plates 18 and 78). This zone is not as easily recognized nor beds are thin, but are close to the surface and adjacent to correlated in the basin. Therefore, it has only been labeled water transportation. Natural brines, which are of great on specific gamma ray logs. importance to Michigan's chemical industry, are present in the carbonates of the Lucas (see Sorensen and Segall, 1970- The correlation of individual salt beds in the Lucas was not Important brine constituents such as iodine, bromine, and attempted. These salt beds are abundant in the northern chlorides of potassium, calcium, magnesium, and sodium are and central portions of the basin and are important extracted and processed to make various chemical economically. A more detailed study of the Lucas would be compounds. helpful in identifying individual salt beds as well as the carbonate beds which contain economically important Accurate correlations of several beds and zones in the Lucas quantities of brine. Formation are fairly easily achieved. But selection of a consistent break between the base of the Dundee and top of the Lucas is not always possible. When radioactivity logs are Amherstburg Formation used for correlation, the contact between the Dundee and Immediately below the Lucas Formation are rocks of the Detroit River Group is generally traced from wells where Amherstburg. The formation was originally defined by anhydrite can be identified to wells in which anhydrite is not Sherzer and Grabau (1909) and includes the beds lying present, and then other significant features must be used to between the Lucas and the Sylvania Sandstone where delineate the units. present. In some areas where the Sylvania is not present, the In the north central portion of the Southern Peninsula the Amherstburg is underlain by the cherty Bois Blanc top of the Lucas (called the top of the Detroit River by most Formation. In southwestern Michigan, the Bois Blanc is geologists) is always placed above the first Detroit River salt absent and Detroit River rocks lie directly on the Bass (see Plate 4). Toward the edges of the basin where salt is Islands as well as other strata of Silurian age. The not present, selecting the top becomes more difficult, Amherstburg is present everywhere beneath the surface in especially in southeastern Michigan. the Southern Peninsula except in the southeastern and southwestern corners of the State, where it has been In the Lucas Formation, several beds and porosity zones removed by erosion. It is composed predominantly of have been correlated. Correlatable horizon DR-1 (see Plate limestone with subordinate dolomite in some areas of the 57) is a bentonite bed which had been previously identified northern and eastern parts of the Southern Peninsula. But it in the Kawkawlin, Michigan area (see Ba1trusaitis, 1970). is all dolomite in the western and southern areas of This bed can be recognized over parts of the basin and is occurrence. A sandstone lentil, found on the west side of the helpful in identifying the upper portion of the Lucas and State and known as the Filer Sandstone, is probably a part of correlating the lower beds. The bentonite shows a the Amherstburg. But there is some debate as to whether distinctively high radioactive reading, and consequently is the Filer is in the Amherstburg or is actually a part of the readily detected. Sylvania. Another bed or group of beds which is identifiable over One of the distinguishing characteristics of the Amherstburg much of the basin is referred to as DR-2 (see Plate 18). Formation is its relatively dark color. It is essentially brown These beds, which are three argillaceous dolomites separated to black fossiliferous carbonate which is more often by anhydrites where they are best developed, have been limestone than dolomite. It can usually be distinguished recognized as consistent and correlatable units by geologists from the overlying light-colored, anhydrite-rich, mostly studying the stratigraphy of the basin. They are significant, nonfossiliferous dolomites of the Lucas. The dark color of especially in central and northern Michigan, because they the Amherstburg has caused many geologists to refer to this directly overly a zone known as the "massive anhydrite" formation as the "Black Lime". In many subsurface sections,

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 16 of 36 however, the dark color becomes lighter downward and the generally confined to the western portion of Michigan. It base of the formation is sometimes difficult to ascertain. appears from correlations, as interpreted in this report, that the Filer is above the Sylvania in the Amherstburg, and is Through the years, several theories have been postulated not directly associated with nor in contact with the Sylvania concerning the depositional environment of the (see also Landes, 1951). Amherstburg. One theory by Gardner (1974) holds that the increasingly dark color upwards suggests a reducing environment which was still able to support diverse and Sylvania Sandstone abundant fauna. The waters may initially have been The Sylvania Sandstone is the basal formation of the Detroit sufficiently aerated to permit sustenance of life; but the sea River Group. It was named by Edward Orton in 1888 from floor became steadily more stagnant due to weakening outcrops in Sylvania Township, Lucas County, Ohio. It is currents, until the corals were buried in the carbonaceous composed predominantly of well rounded and sorted, fine lime muds. The faunas flourished during the early to medium grained sandstone with lesser amounts of silt, transgressive phase of the Amherstburg. Then, with chert and carbonate. The Sylvania Sandstone is not found cessation of transgression, intermittent stagnation occurred, everywhere in the Michigan Basin; it is located in portions of as evidenced by the dark coloration and excellent northwestern, central, and southeastern Michigan (see preservation of in the black limestone facies. Water Landes, 1949 and 1950. The sand body is 50 to 75 miles depths probably remained within the zone of wide, and over 300 feet thick in the center of the basin. In photosynthesis; but decreased circulation of the water led to several areas Sylvania Sandstone is an important brine several periods when life could not exist. producer. Correlation of the Amherstburg over much of the basin is The depositional history of the Sylvania has been a subject possible because in many areas the formation exhibits of disagreement among earth scientists. Some geologists slightly higher radioactivity than most of the surrounding assert that because of the facies gradation between the rocks. Many of the cross-sections show three correlation Sylvania sands, the Amherstburg carbonates, and the cherty lines associated with the Amherstburg (see Plate k). The Bois Blanc, a marine depositional environment is a logical upper line depicts the top of the Amherstburg as it is supposition. Others believe that both eolian and fluvial defined in this report. The black limestone typically processes supplied sand to the seaway where it was identified as Amherstburg was chosen to be the top of the redistributed by marine currents and deposited along coastal formation, and was found in several wells at this point. The areas concurrently with offshore carbonates of the Bois middle line denotes a correlatable marker, which has, in the Blanc and Amherstburg. Sherzer and Grabau (1909) past, been designated as the top of the Amherstburg. It is postulated an eolian origin for the Sylvania while Carman another usable correlation point; but if this is chosen as the (1936) suggested a reworking of eolian sands by marine top of the formation, the upper black limestone as well as waters. the "Filer Sandstone", a part of the Amherstburg, would not be included in the formation. Finally, the lower line defines Correlation of the Sylvania Sandstone in the central portion the base of the Amherstburg, which can be recognized of the basin is shown in cross-section A-M, Plate 72. The readily when underlying Sylvania Sandstone is present. low radioactivity reading of the sand relative to the However, where the Sylvania is not present, or when an carbonates occurring above and below it allows for attempt is made to correlate in southeastern Michigan, bracketing of the Sylvania with some degree of accuracy. problems develop in choosing the proper gamma ray On the edges of the depositional area, however, correlations response in order to delineate the base of the formation. become more speculative due to a decrease in sand deposition and also a decrease in the variability of the If the gamma ray curve response supposed to represent the radioactive response between the Sylvania and the Amherstburg in northern, western, and central Michigan is surrounding strata. correlated carefully into southeastern Michigan, 50 feet or more of sand seems to be present above the Amherstburg, Plate 26 shows that the Sylvania slowly loses its as shown in cross-section A-L (Plates 66 and 67, the characteristic low radioactivity in northwestern Michigan as Messmore No. 1, Lopez No. 1, and Jorgensen No. 1). The more and more carbonate is introduced into the formation. Sylvania in many areas of the State contains carbonate beds Sample analysis by the writer confirms that the Sylvania is and it may be that the Amherstburg is one of them, or an present in the area as depicted on Plate 26. abundance of sand is found above the Amherstburg in Some sand is found in the southwestern portion of the southeastern Michigan. Southern Peninsula which may also be the Sylvania (see In western Michigan, the Filer Sandstone exists in the upper Plate 52). Since the classification is still questionable, the portion of the Amherstburg. This sandstone is identified as Sylvania shown on the plates is qualified with a question associated with the Amherstburg, and the log curves of mark. several wells (see Plate 25) indicate this. The Filer is

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 17 of 36 Bois Blanc Formation been correlated or identified with a very low-radioactive zone just above the Bass Islands. The current data shows The Bois Blanc is the basal formation of the Devonian that the Bois Blanc may include some of the carbonates with System generally recognized in the Southern Peninsula. The higher radioactive readings which occur above this low- name was introduced by Ehlers (1945) to apply to 360 feet radioactive zone (see Plates 26 and 31). Correlations of strata on Bois Blanc Island in the extending from the central basin area where a full section of region. In the subsurface, the cherty Bois Blanc carbonates Bois Blanc is present to the western part of the state appear are interbedded and gradational with Sylvania sandstones, or to verify this conclusion. In the southern part of the State, the Amherstburg where the Sylvania is not present. Studies correlation of the Bois Blanc is complicated by changes in of wells drilled in the central basin area in Ogemaw County lithology, thinning of strata above and below the formation, have revealed that the Bois Blanc may be over 800 feet thick and erosional unconformities. As shown on Plates 40, 46 (see Plate 4, the State-Foster No. 1). The thickness and 52, the Amherst-burg, Sylvania, Bois Blanc and Bass decreases from the central basin area to the north and Islands thin in a south and southwesterly direction and some northwest, where it may be about 300 feet thick in Leelanau of their radioactive characteristics change. The Bois Blanc County, and to the southeast where it disappears in Monroe eventually disappears in southern Michigan due to erosion, County. The Bois Blanc Formation is absent in the as seen on Plates 46, 52 and 58. In following the lithologic southwestern and southern counties. characteristics of the Bois Blanc into southern Michigan, No discussion of the Bois Blanc Formation would be chert can be found in some of the cuttings at a depth where complete without mention of the Mackinac Breccia. Masses the Bois Blanc should be located according to radioactive of indurated breccia are left standing as scenic chimney characteristics on gamma ray logs. This adds more credence rocks, pillars and arches in the Straits region. The breccia to correlation of the Bois Blanc into southern Michigan. contains rocks of Bois Blanc age as well as blocks and fragments from the Detroit River Group, and the Bass Islands and Salina groups of Silurian age. The Mackinac Silurian System Breccia is the most prominent rock in the Straits area in the northern part of the Southern Peninsula and the southern Silurian age rocks lie beneath Devonian strata in the tip of Mackinac County in the Northern Peninsula. Michigan Basin, separated from them by an unconformity in many areas. In descending order the Silurian rocks are According to Landes (1945) the Mackinac Breccia formed divided into the Bass Islands Group, Salina Group, Niagara by leaching of Salina salt and subsequent collapse of the Group, Cabot Head Shale, and Manitoulin Dolomite. The overlying rocks. Leaching occurred during emergences of Salina Group is further subdivided into informal units, the the land in the Straits area after the salt had been deposited. G Unit, F Evaporite, E Unit, D Evaporite, C Unit, B Percolating underground water was the most probable cause Evaporite, A-2 Carbonate, A-2 Evaporite, A-l Carbonate, of leaching great quantities of salt from the Salina deposits. and A-l Evaporite. The Silurian strata contain vast amounts A number of caves and caverns were produced where the of salt, and hundreds of pinnacle reefs. These strata are salt was above the groundwater table. These underground important economically because of the limestone, dolomite, caves initiated a condition of instability which led to the salt, and oil and gas which are obtained or produced from collapse of the cavern roofs. The overlying rock fell and slid them. downward and eventually came to rest in jumbled fashion. Thus rocks of different formations and varying ages were Bass Islands Group brecciated and tumbled together. Some parts of the breccia were later indurated. The age of brecciation was at least The Bass Islands Group was named for several islands near post-Bois Blanc and is probably post-Detroit River and pre- the western end of , where rocks of the group Dundee. outcrop. In southern Michigan (Monroe County), Bass Islands rocks are divided in outcrop into Raisin River The Bois Blanc can be correlated accurately over much of Dolomite and Put-in-Bay Dolomite, but these formations the central basin area. As shown on Plates 11, 26 and 67, the are seldom separated in the subsurface. In the Straits of Bois Blanc, because of its slightly higher radioactivity, can be Mackinac region, northern Michigan, Bass Islands rocks in distinguished from the overlying Sylvania. In northern outcrop are called St. Ignace Dolomite. Michigan, where Sylvania Sandstone is not present, the Bois Blanc can generally be differentiated from the overlying In the northern part of the Southern Peninsula, the Bass Amherstburg by its lower radioactivity and higher porosity Islands rocks are about 325 to 350 feet thick, while in the (see Plates k and 18). center they attain a thickness of approximately 575 feet. In Presque Isle County the top of the Bass Islands is about 500 In western and southern Michigan, however, the Bois Blanc feet below sea level while in Alpena County it drops to Formation has been removed by erosion and is not well about 900 feet and in Midland County it is more than 4200 defined. In western Michigan, the formation previously has feet below sea level. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 18 of 36 Bass Islands rocks in the subsurface are typically dense, buff generally of gray dolomitic shale and can be readily dolomites which are sparsely oolitic in the upper portion. distinguished from the light-colored Bass Islands rocks Lower in the section gray argillaceous dolomite is above. As the G Unit is traced to the basin margins, it thins intermingled with buff dolomite, and in the interior part of and becomes less argillaceous, and in the extreme southern the basin several thin anhydrites and salt beds are present. portion of the Southern Peninsula it cannot be distinguished The contact between the Salina and Bass Islands rocks is from Bass Islands rocks by using gamma ray logs. generally considered to be transitional and conformable. The G Unit in the center of the basin is characterized by However, an unconformity exists between the Silurian and high radioactivity as shown on Plate 5. When this unit is Devonian in many parts of the basin and especially over traced into southern Michigan (see Plate 58), it thins large portions of southwestern Michigan. In this region the markedly and eventually becomes unrecognizable at the Devonian formations lie upon successively older and southern margins. In the past many geologists arbitrarily stratigraphically lower units of the Salina Group. In the picked the top of the Salina in southern Michigan at the extreme southwestern corner of Michigan the Salina has massive radioactive zone which occurs beneath the point been completely removed and Devonian rocks lie directly where the present G Unit is chosen (see Plate 58, Crawford upon the Niagaran. The extent of the erosional truncation in No. 1, at a depth of approximately 2680 feet). However, the this region appears to be related to the thick Niagaran reef G Unit, although thin, can be recognized in many areas at complex on the Indiana-Ohio platform and the Kankakee the edges of the basin and should be defined as shown in Arch. In this region the truncation is greatest where the sections. The G Unit, along with many of the Salina Niagaran rocks are thickest. Where the Niagaran reef formations, has been removed by pre-Devonian erosion in complex is thinnest, the truncation is less pronounced and a southwestern Michigan (see Plates 46 and 53). This thicker section of Salina-Bass Islands rocks is preserved. unconformity has been discussed by Ells (1958, 1962, and Correlation of Bass Islands strata is fairly routine where a 1967a) and is an important feature in delineating the full section of the formation is developed. In southern geological history of this portion of the basin. The use of Michigan, however, thinning due to depositional phenomena gamma ray logs facilitates more accurate correlation for this and Bass Islands erosion make correlation less secure. As area, thus verifying the existence of the unconformity. shown on Plate 58, the Bass Islands in the southern area The next lower formation of the Salina Group is the F becomes thinner, but still contains some beds which are Evaporite. A succession of pure and impure salt beds, thin slightly more radioactive, and can be correlated. But in anhydrites and anhydritic shale beds, shaly dolomites and southwestern and extreme southern Michigan (see Plates 46, dolomites comprise the F Evaporite. The shales are 52 and 58), these beds are not present and correlation generally gray, greenish gray and reddish gray, while the becomes speculative at best. dolomites are gray, buff, and brown. The F Evaporite thins from 970 feet in Ogemaw County to zero thickness in Salina Group portions of southwestern Michigan, having been completely Subsurface units of the Salina Group occur below the Bass removed by erosion. The thinning is due mainly to a Islands dolomite in Michigan. Salina Group rocks were decrease in salt deposition in a south-westward direction and separated by Landes (1945b) as Units A upward through H, eventual pinchout of the salt; but thinning of the shale and with Unit H being equivalent to the Bass Islands. The A dolomite beds also occurs. Units were later modified by Evans (1950). Subsequent The F Evaporite has been subdivided into six convenient exploration in Michigan has brought about a more detailed units: F salt 1 upward to F salt 6 which are based on gamma subdivision of the strata. Most of the subdivisions are based ray-neutron log curves (Ells, 1962 and 1967) (see Plate 5). on gamma ray log curves which can be traced over a great They may not be recognized in all localities through sample portion of the basin. The name "H Unit", as applied by studies, although they are usually distinguishable upon Landes to the Bass Islands rocks, has been dropped and meticulous examination of good samples. The six units are Bass Islands is now in standard usage. The G Unit, as evident on gamma ray logs and are very useful in originally described, has undergone a revision of definition stratigraphic correlation of Salina beds. and is now designated in a different manner. The point where the unit was previously located on logs from wells on As seen on Plates 58 and 63, the evaporites are lost in the margins of the basin was shown to grade basinward into southern Michigan and the shales and carbonates remain; the F Evaporite. Present practice is to call the top of the G and these entities are correlated in this area. The evaporites Unit in the center of the basin at the point which geologists are also lost in the extreme northern part of the Southern previously called the "H Shale". For a more detailed Peninsula. As seen on Plates 12, 19 and 26, the evaporites discussion of the Salina Group see Ailing and Briggs (1961). extend northward a greater distance over the Niagara barrier reef than they do in southern Michigan. This observation is The G Unit is the uppermost formation of the Salina an important feature in delineating overall evaporite Group. In the center of the Southern Peninsula it consists deposition in the Michigan Basin.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 19 of 36 The F Evaporite sequence is underlain by the E Unit, a of shale and dolomite in extreme southern Michigan (see series of gray, greenish-gray, and red shales interbedded with Plates 53 and 59, the Clark No. 1 and Laser No. 1 wells). thin dolomites. The unit ranges from 90 to 120 feet thick, The A-2 Carbonate lies sequentially beneath the B but has been removed by erosion in much of southwestern Evaporite. It is composed of dark to light colored Michigan. On the western side of the basin a porous limestones and dolomites. Where it overlies the reef dolomite occurs near the base. This porous zone grades complex on the margin of the basin, the A-2 Carbonate is eastward and basinward into shales. The porous dolomite, usually dolomite. In the central part of the basin some called the "E Unit" or "Kintigh Zone" (see Plate 52), has poorly developed anhydrite beds occur within the A-2 produced some oil. The E Unit when compared with the Carbonate. The basal part of the formation contains some overlying F Evaporite remains fairly constant in thickness carbonaceous partings in the limestone or dolomite which because of its general lack of evaporites. are similar to the "poker chip" shales of the A-l Carbonate, a The D Evaporite, encountered beneath the E Unit, is a sa1t stratigraphically lower unit. In much of the central basin bed which averages about 40 feet in thickness. The unit is area, the A-2 Carbonate maintains an average thickness of split by a thin dolomite bed which causes a consistent 150 feet but thins to less than 100 feet in the southern and deflection on gamma ray logs. When all of the evaporite northern parts of the Southern Peninsula. Near some of the units in the basin are examined, the D Evaporite appears to pinnacle reef development in southern and northern have the smallest areal extent in Michigan, and appears to be Michigan the formation becomes anomalously thick, limited to the basin interior. The D Evaporite gamma ray attaining as much as 275 feet of beds. In southwestern log curves can be followed with a great degree of accuracy Michigan it has been removed by erosion. over the depositional area, making the unit one of the most Oil and gas have been produced from the A-2 Carbonate. easily recognized Salina units in Michigan. In some counties in southwestern Michigan the upper part The C Unit, below the D Evaporite, is one of the most of the formation consists of porous dolomite while the widespread of the Salina units. It can be traced throughout lower portion is shaly limestone. Gas has been produced most of the Southern Peninsula and may be traced as far from the porous dolomite where conditions for entrapment east as New York (Ultieg, 1963). It is a gray shaly dolomite are favorable. It is very likely that the A-2 Carbonate will averaging about 60 feet in thickness but in some wells or produce more gas and oil in the future. localized areas it may be over 120 feet thick. No salt beds Correlation of the A-2 Carbonate is fairly simple and are found in this unit; but a thin bed of nodular anhydrite or straightforward over much of the basin because it is dolomite is present which persists over a large part of the generally bracketed by two evaporite units, the B Evaporite basin. above and the underlying A-2 Evaporite. However, in areas The C Unit is important to this study because of its where these evaporites are not present, especially in widespread occurrence in the Michigan Basin. It is used as southern Michigan, the correlations are somewhat more the datum for correlating all of the Silurian strata in this speculative. report. As shown on the plates pertaining to the Salina The thickness of the A-2 Carbonate and selection of the Group, the radioactive characteristics of the C Unit are base over the southern reef bank is debatable among some constant except for a small area in southern Michigan where geologists. These correlation sections delineate the A-2 the unit becomes abnormally thick (see Plate 52) and a part Carbonate radioactive characteristics and follow them as far of extreme northern Michigan where it thins markedly (see and as accurately as possible from the center of the basin Plates 19 and 27). into southern Michigan. As depicted on Plates 59 and 6k, The B Evaporite underlies the C Unit and is composed the unit loses many of its characteristics when traced from predominantly of salt in the lower part and a series of salt, the center of the basin southward, and correlation becomes shale, and dolomite beds in the upper half. It is over 475 difficult. However, the unit appears to show somewhat feet thick in the central portion of the basin and less than 50 higher radioactivity than some of the surrounding strata, and feet thick in the southern Niagaran reef complex. Toward this is helpful for identification. the southern margin of the basin the B Evaporite thins In northern Michigan also the A-2 Carbonate is difficult to because of pinching out of the lower salt. Salt beds that lie correlate in some areas because of the loss of overlying and between thin dolomite layers grade to anhydrite and underlying evaporites. This is especially true of the base of eventually pinch out. In the southern portion of the basin the formation (see Plate 13). However, it does maintain where the B Evaporite is thin and anhydrite is not present, some of the radioactive characteristics, and can be separated the unit is not easily distinguishable from the underlying A-2 from underlying units with a greater degree of assurance Carbonate on gamma ray logs; but an attempt is made to than in the southern portion of Michigan. The formation is delineate the unit in these regions. According to radioactive characterized by a slightly more radioactive base in some characteristics, the B Evaporite is composed almost entirely portions of northern Michigan, as shown on Plate 27.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 20 of 36 The A-2 Evaporite, which underlies the A-2 Carbonate in Oil and gas are produced from the A-l Carbonate in much of the basin, is predominantly pure salt in the center Michigan. The formation produces not only in association of the State. In this area it is more than 475 feet thick, with Niagaran pinnacle reefs, but also in other areas where grading laterally into anhydrite near the margins of the basin favorable entrapment conditions exist. The A-l Carbonate is and eventually pinching out. Where the A2 Evaporite is all generally a dolomite in those areas where production is salt, it is common practice to call it the A-2 salt; where it is obtained. all anhydrite, the term A-2 anhydrite is applied. The A-l Carbonate is easily correctable in central Michigan, In areas where pinnacle reefs are encountered, the A-2 as are most of the other Salina Units. Difficulties arise, Evaporite may thin drastically over the pinnacle and is however, in distinguishing the formation in northern and generally anhydrite. Near the depositional edge of the A-2 southern Michigan. As shown on Plates 13 and 20, the A-2 Evaporite, either solution or migration of the salt has Evaporite is not present in northern Michigan, and the A-2 occurred. Either of these events could serve as a Carbonate and A-l Carbonate are in contact. The premise mechanism for developing structure in overlying beds which for separation of the two is the slightly higher radioactivity in turn could result in the entrapment of oil and/or gas. shown at the bottom of the A-2 Carbonate. The base of the Some pools in southwestern Michigan are related to this A-l Carbonate is also difficult to define in this area. Plates phenomenon (Ells, 1967). 13, 20 and 27 show that the radioactive variations between the A-l Carbonate and underlying Niagara are very subtle. The correlation of the A-2 Evaporite is relatively The writer believes that the base is at or near the area straightforward where the unit exists. It can be delineated selected in the correlation sections. accurately where a full section is present, and can be followed to areas where it pinches out in northern and In some areas of southern Michigan, A-l Carbonate southern Michigan, as shown on Plates 20 and 53, correlation is also speculative. Judging by the radioactive respectively. characteristics of the unit, the writer believes that although the base of the A-l Carbonate is open to speculation, it is The A-l Carbonate, the next unit encountered, is similar to near the zone selected on Plates 53 and 59. It does not the A-2 Carbonate in that it is essentially a dark colored extend into extreme southern Michigan. limestone or dolomite, or both. The basal portion in some places contains thinly laminated dolomite separated by The A-l Evaporite is the lowermost formation of the Salina carbonaceous partings, possibly suggestive of cyclic Group. In the center of the basin it is predominantly salt, deposition in deep or quiet water. These laminated intervals but toward the margins it grades into anhydrite. It achieves are similar to beds found in the A-2 Carbonate, which are a thickness of 475 feet in the central portion of the basin, also termed "poker chip". In some southern portions of the but gradually pinches out near the reef complex. It is basin where pinnacle reefs are existent, thin anhydrite beds generally absent over the crests of pinnacle reefs, but may be may also be present within the A-l Carbonate. These two, present on the reef flanks as anhydrite. and sometimes three, beds of anhydrite are termed "rabbit The upper and lower limits of the A-l Evaporite can be ears" by well-site geologists (see Plate 53, Midlam No. l), and outlined reasonably well over most of the basin. Where the they are sometimes indicative of reefing in the vicinity. The formation changes from salt to anhydrite on the basin anhydrite beds have in some cases been confused with the margins it can be delineated by its lesser gamma ray underlying anhydrite equivalent of the A-l Evaporite. radioactivity and the characteristic anhydrite response on The thickness of the A-l Carbonate is generally least in the neutron logs. These characteristics can be used to follow basin interior and greatest around the inner margin of the the formation into northern and southern Michigan areas basin where pinnacle reefs occur. Over a large part of where it eventually pinches out (see Plates 27 and 59, central Michigan this unit ranges between 50 and 75 feet respectively). thick, whereas in some portions of the pinnacle reef belt it Sylvinite beds occur within the A-l Evaporite in the central achieves a thickness of 100 to 125 feet. The thickness may part of the basin (see plates 6, 13 and 20). The sylvinite, be biologically controlled by masses of algal material near according to Matthews and Egelson (1974), is a mixture of pinnacle reef development. The unit is sometimes absent sylvite (KCl) and halite (NaCl), and underlies some 13,000 over tall reefs and may be missing over the reef bank square miles of Michigan. This potash facies occurs as a lens complex. Where the A-l Evaporite is not present below the within a lenses of halite and the potash increases in thickness A-l Carbonate, it may be difficult to separate the A-l and purity basinward. It may also be found at the base of Carbonate from Niagaran rocks. But in some cases the A-l the A-l Carbonate as shown on Plate 6, Garland No. 1. The Carbonate can still be recognized on gamma ray log curves sylvinite portion may be distributed through as much as 140 where the formation occurs over pinnacle reefs and feet of aggregate thickness of A-l Evaporite, with individual associated with the reef bank, as illustrated on Plates 53 and beds being much thinner. Potassium values when measured 64, the Midlam No. 1 and the Grau No. 1. as l<20 are as high as 40 to 45 percent in some individual beds. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 21 of 36 It is of interest to note that evidence of apparent faulting in carbonate sedimentation rates were lower than along the the A-l Evaporite and Niagaran sections of rock has been margins. The barrier and pinnacle reef complexes around found in a well drilled in Sanilac County (see Plate 80). The the basin margins produced hundreds of feet of carbonate well is the Humble Oil and Refining Company's Hoppinthal rock. No. 1, located in the C NE, NE, of Section 16, T19N, RI5E, The Niagara carbonate sedimentation rate gradient may also Fremont Township, Sanilac County. A description of the explain the distribution of hematite staining in the Niagara zone, submitted in 1964 by the company along with the well rocks (Mesolella, 197,0. Mesolella reports a suggestion by A. logs, follows: G. Fischer that small amounts of limonite were precipitated The No. 1 Hoppinthal encountered a basically normal throughout the basin in conjunction with Niagara carbonate section except in the lower Silurian where 701 of A-l salt and deposition. Where the sedimentation rates were high along Niagaran dolomite were repeated. After drilling a normal A- the margins, the limonite was buried and underwent l salt and 38' of underlying Niagaran, a reverse fault was reduction to form such iron minerals as pyrite. In the basin crossed, and the well encountered 32' of additional A-l salt interior, however, low sedimentation rates resulted in slow before topping the Niagaran for a second time at 4736 feet. burial of organic material and destruction of the material by bacterial action. Therefore, organic material generally was Niagara Group absent from these sediments and limonite was preserved and dehydrated to form hematite. Beneath the lowermost A-l beds of the Salina are rocks of the Niagara Group of Middle Silurian age. The Niagara In Michigan, the lowermost portion of the Niagara group of consists of carbonate beds in the upper portion and Middle Silurian age is generally referred to as the Clinton. carbonates, argillaceous carbonates, shales and chert in the These rocks can readily be identified on gamma ray logs in lower portion. The lower portion, generally referred to as most of the southern part of the State, but in the northern the Clinton, is thought to be equivalent to the Manistique Southern Peninsula they are difficult to distinguish from and Burnt Bluff Groups which are exposed in the Northern overlying strata. Although proper usage of the term Peninsula (see Chart l). The upper portion of the Niagara "Clinton" has been a subject for debate, the term has been Group is not designated by a formal formation name in the applied for many years by geologists working in the State. subsurface, but it is generally correlated with the Engadine, In southern Michigan, the Clinton is generally identified by exposed in the eastern portion of the Northern Peninsula. its argillaceous nature as well as its higher gamma ray Pinnacle reef buildups in Michigan may sometimes be radioactivity (see Plate 73). It is composed of gray to green present in the upper portion of the Niagara Group. This shales, tan to brown, finely crystalline dolomite and segment is generally separated into three lithologic units in argillaceous dolomites. the subsurface according to oil field terminology. In In northern Michigan the Clinton is no longer argillaceous, descending order they are: the "Brown Niagaran", the "Gray but becomes a massive carbonate containing some chert Niagaran", and the "White Niagaran". Subdivision into beds. It is not as radioactive as in southern Michigan (see these units is based mainly on color, texture, and Plate 6). An interesting and important feature of the stratigraphic position. According to many geologists, most formation is the difference in thickness from the southern to of the pinnacle reef buildup occurred during the time when the northern part of the Southern Peninsula. In the south, Brown Niagaran beds were deposited. these strata are generally 50 feet or less. In the northern The upper Niagara rocks which are nonreef but are near the portion of the basin, however, these rocks may be over 400 barrier and pinnacle reefs consist of tan to gray, dense, feet thick. The change in thickness and lithology is gradual. argillaceous, micritic fossiliferous carbonates. Toward the More information concerning the Niagaran in northern interior of the basin, the nonreef Niagara is still a dense, Michigan is found in Shelden (1963). argillaceous, fossiliferous carbonate, but it thins markedly The Niagara rocks have yielded large quantities of oil and and also displays a mottled reddish-brown coloration due to gas. Most of the hydrocarbon accumulations are confined the presence of hematite. Thinning in the basin interior may to the pinnacle reefs in the upper portion of the Niagara be attributed to a lack of organic buildups away from the Group. These pinnacle reefs have been discovered reef belt. throughout much of lower Michigan just basinward from According to Mesolella et al. (197,0, the Michigan Basin was the barrier reef complex. The reefs may be up to several characterized by open circulation and normal marine salinity hundred feet high and may cover as much as 1000 acres or during Niagara deposition. A barrier reef complex built as little as kO to 60 acres. The reservoir rocks, having principally by stromatoporoids flourished around the rim, intercrysta11ine and vugular porosity, are dolomitized and a belt of coral pinnacle reefs existed immediately remains of reef-building organisms. Porosity and basinward of the barrier-reef complex. In the basin interior permeability values vary considerably within a single reef and the processes of organic reef building were negligible and between individual reefs, but the porosity averages about eight percent and permeability about 27 millidarcies. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 22 of 36 The top of the Niagara in the center of Michigan's Southern shown on Plates 6, 13 and 20. It also thins, but not to the Peninsula can be correlated easily because of the overlying degree that occurs in southern Michigan. In northern A-l Evaporite. Around the edges of the basin, however, the Michigan, recognition of the limits of the formation is formation is less identifiable. The top of the Niagara in complicated by the proximity of other argillaceous beds and southern Michigan is chosen at the base of the last a lack of deep control in that area. radioactive bed in the A-l Carbonate, as shown on Plates 47 and 64. When many more logs are inspected than the Manitoulin Dolomite number shown on the cross-sections, this correlation point can be traced over much of southern Michigan. The base of the Silurian System is represented in Michigan by the Manitoulin Dolomite. It is typically a thin- to thick- Distinguishing the top of the Niagara Group is sometimes bedded, gray-to buff-weathering dolomite. On a fresh difficult in many areas of northern Michigan. The technique surface it is sometimes light blue-gray. In southeastern used in this study was tracing characteristics of the A-l and Michigan the formation is predominantly dolomite; but in A-2 Carbonates above, and some of the strata beneath the northern Michigan some shale beds become prominent in top of the Niagara. Approaching the basin edge, the the unit. Like the Cabot Head, the Manitoulin thins in a overlying units become thinner and some changes in facies westerly direction, and in some areas it cannot be (i.e., rocks become slightly more argillaceous), and thus differentiated from the Cabot Head. some changes in log characteristics (higher radioactivity), occur (see Plate 13, White and Burns No. l). This method For these cross-sections, the Manitoulin, like the Cabot proved most helpful in selecting the top of the Niagara in Head, was first compared with the formation in Ontario for northern Michigan. definition and then carried into southeastern Michigan. As the Manitoulin is correlated from the area of St. Clair As shown on Plates 47, 53, 59, 64 and 68, the Clinton is County to the west and southwest, the formation thins, as defined by higher radioactivity than the overlying strata in shown on Plates 73, 68, 64, 59, 53 and 47. In a northerly southern Michigan. This signifies that the rock is more direction it changes character, exhibiting greater radioactive argillaceous and these higher radioactive curves can be tendencies and thus more argillaceous content (see Plates 6, followed over much of southern Michigan. Tracing these 13 and 20). However, it does not thin toward the northern higher radioactive beds into northern Michigan, however, a part of the State as much as in southern Michigan and is, decrease in radioactivity is noticeable along with a marked therefore, easier to identify in northern Michigan. thickening of the strata.

Cabot Head Shale Ordovician System The Cabot Head Shale occurs stratigraphically below the The Ordovician System is the next older rock sequence in Niagara Group. In the subsurface of southeastern Michigan the Michigan Basin. Ordovician rocks are found in the the Cabot Head consists of red, greenish-gray and gray subsurface throughout the Southern Peninsula and in the shales. As the formation is traced westward across the State, southeastern portion of the Northern Peninsula. They it becomes progressively less argillaceous and is thinner in outcrop in an arcuate belt in the Northern Peninsula. the southern portion of the Southern Peninsula. In the northern part of the basin it contains some anhydrite, and is The uppermost group of the system in the subsurface is the generally thicker and more argillaceous than in western Richmond. As shown in "Stratigraphic Succession in Michigan. Rather slow sedimentation probably Michigan" (Chart 1), the Queenston Shale and Utica Shale characterized the period during which the shale was are sometimes separated from the Group. General practice, deposited. however, is to call all of the Richmond Group the Cincinnatian (a time-stratigraphic term) in the subsurface; The Cabot Head Shale can be correlated in the subsurface this study follows that practice. over the entire Southern Peninsula. The formation was initially defined in southeastern Michigan and compared In descending order, the next strata are the Trenton and with a well in Ontario in which the Cabot Head was Black River groups. They are not subdivided into individual delineated. It was then correlated in a westerly and northerly formations in the subsurface, but are generally distinguished direction from this point. As shown on Plates 68, 64, 59, 53 as separate entities throughout the Southern Peninsula. The and 47, the Cabot Head exhibits a less radioactive and thus basal member of the Black River Group, the Glenwood, is less argillaceous character in a westerly direction. It is also identified in this report and correlated throughout the basin. thinner in this direction, but the radioactive characteristics The St. Peter Sandstone has formation status and underlies still remain similar so that correlation is possible. the Black River. The St. Peter is not found in the entire In a northerly and northwesterly direction the Cabot Head is basin, however, having been removed by erosion in some characterized by an interbedding of shales and carbonates, as localities, and it is not delineated in this report.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 23 of 36 The oldest group of Ordovician strata is the Prairie du As shown on the sections, the upper part of the Chien. It is divided in the subsurface into three formations Cincinnatian has been separated into 5 correlatable units, which, in descending order, are the , the CS-Unit 1 through CS-Unit 5. These are not exactly the New Richmond Sandstone, and the . In same units as those shown by Nurmi (1972) in his many areas these formations cannot be distinguished, and in unpublished Master's thesis. Plate 7 shows that the several parts of the basin they are absent due either to Cincinnatian, where it is well developed, is a series of shales erosion or nondeposition. They are not, therefore, or highly argillaceous materials denoted by high delineated on the correlation sections. radioactivity, and limestones and/or dolomites denoted by low radioactivity. Many of these units can be followed Cincinnatian Series accurately through the central basin area, but at the outer edges some of the units are less distinct. The first sequence of Ordovician sediments in the subsurface is the Cincinnatian Series. Red sediments at the Plates 7, 14 and 21 in the northern part of the basin show top of the Series are sometimes identified as Queenston that the upper unit, CS-Unit 5, is thicker in this area and Shale. The Cincinnatian is composed of shales, argillaceous possesses slightly different radioactive characteristics than it limestones or dolomites, and relatively pure limestones. has in the center of the basin. As this unit is followed to the Individual beds undergo facies changes in various parts of center of the basin and southward (Plate 60), a noticeable the depositional area and these facies can, in many cases, be thinning, caused by an apparent unconformity, occurs. traced by using gamma ray logs. An erosional unconformity In the southwestern portion of Michigan, as shown on at the contact between Silurian and Ordovician sediments Plates 46 and 54, the Cincinnatian thins significantly and the exists in some areas of the basin. Separation of the Silurian character of the radioactive response changes. In this and Ordovician systems is difficult in some localities because southwestern direction, erosion has stripped away some of of the unconformity. the upper strata. As the units are followed into southeastern An unpublished thesis study by Nurmi (1972) showed that Michigan it is also evident that an unconformity is present at the Cincinnatian could be divided into units. He divided the the top of the Cincinnatian, and some of the upper strata Upper Ordovician, including the Utica shale, into six have been removed (see Plate 65). separate units. The Utica was designated "unit one" and the Plate 7, the Sparks, Eckelbarger, Whight-sil No. 1-8 well, remaining five units comprised the Cincinnatian. Nurmi 's shows an argillaceous unit (CS-Unit 1) which is quite study revealed that many of the units could be correlated difficult to distinguish from the underlying Utica Shale. As over large portions of the basin; and the current this unit is traced to other parts of the basin it thins and investigation tends to corroborate this fact. Nurmi also contains much more calcareous material (see Plates 14, 28, showed that the uppermost unit he defined was missing in 48 and 60). several portions of the basin. CS-Unit 5 of this report, the uppermost unit of the Cincinnatian, can be easily recognized Radioactive characteristics of the middle units (CS-Units 2, 3 in the central portion of the basin. Where the unit is present and 4) of the Cincinnatian remain more constant than those in the central and southern portions of the basin it contains of the upper and lower units. As shown on the sections, the some red shale. Progressing in a northward direction, thicknesses of the middle units also remain fairly constant however, carbonate stringers appear and increase in number. throughout the basin, with only minor changes on the In some areas near the margins of the basin some of the periphery. These changes in thickness can be noted on upper strata have been eroded, and the carbonate beds Plates 21, 48, 54 and 65. which occur below the unit are scarcely distinguishable from the Silurian Manitoulin Dolomite above. Utica Shale Other units delineated by Nurmi (1972) and those shown as The next Ordovician formation, beneath the upper units of correlatable units in this study are composed, in many areas, the Cineinnatian, is the Utica Shale. It is uniformly gray to of inter-bedded shales and carbonates. The lithology of dark gray shale with minor amounts of green shale in the these units is quite variable due to facies changes which upper portion and some black shale just above the Trenton. occur throughout the basin. In some limestone stringers occur in the middle of the uni t. These various facies can be correlated if careful sample studies are made, but gamma ray logs show the correlation The Utica is variable in thickness, ranging from 200 feet in of these facies in a more precise manner. Cohee (1948) and western Michigan to as much as 400 feet in southeastern Nurmi (1972) have described the depositional history of the Michigan. There also appear to be areas in the basin where Cincinnatian. Such information is valuable and necessary the unit is anomalously thin or thick. These occurrences for an understanding of the lithologic changes which occur apparently are related to subsurface structures such as the throughout the basin. Howel1 anticline in Livingston County, where the Utica is anomalously thin. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 24 of 36 As shown in the cross-sections, the Utica retains its high In the northern part of the basin, the Trenton is somewhat radioactive response throughout Michigan. It is easily more difficult to bracket because it becomes thinner and is correlatable because of the sharp break with the underlying more highly radioactive. The upper portion especially shows Trenton, which shows low radioactivity, and the overlying significantly higher radioactivity (see Plates 14 and 21). The upper portion of the Cincinnatian, which is less radioactive correlatable bed labeled TG-1 can be followed over a large than the Utica (Plates 5k and 60). Because of the distinctive, portion of the basin and is an aid in correlating the Trenton sharp contact between basal Utica and the top of the Group. Trenton Group as shown by the log curves, the base of the Utica Shale was used as a datum for correlating both Black River Group underlying and overlying strata. The Black River is the lowermost group of Middle Trenton Group Ordovician strata in the Southern Peninsula. The lithology of the Black River is similar to that of the Trenton, Trenton rocks of Middle Ordovician age underlie the Utica predominantly a brown to gray limestone. Like the Trenton Shale throughout the Southern Peninsula. The Trenton Group, it also appears to be more argillaceous in the generally is undivided in the subsurface; but it is separated northern part of the Southern Peninsula. A distinctive bed into two formations in the Northern Peninsula, where it found near the top of the Black River in parts of southern outcrops (see Chart 1). In the Southern Peninsula it ranges Michigan is called the "Black River Shale". It is a thin shale from about 200 to near 475 feet in thickness. Structure bed that induces a characteristic curve on gamma ray logs contours on the top of the Trenton Group show about (see Plate 5,0). It is widely used as a marker for mapping 11,000 feet of relief from the outcrop area in the Northern purposes. Peninsula to the center of the basin near Clare and Gladwin The thickness of the Black River Group in Michigan varies counties. from about 150 to 500 feet. It is generally thickest in the In the subsurface the Trenton is composed predominantly central and southern portions of the basin and thins in a of light-brown to brown and gray fossiliferous, finely northerly direction. Near the Albion-Scipio trend area the crystalline to medium crystalline limestone (see Cohee, thickness is fairly constant, ranging from 239 to 247 feet. 1945b). In the northern portion of the Southern Peninsula At the base of the Black River Group is a member referred the Trenton becomes increasingly argillaceous. It is also to as the Glenwood Shale. This unit, according to DeWitt generally more argillaceous near the base. Dolomite may (1960), is composed of dolomitic sandstone, sandy and silty occur in the section, but it is usually confined to areas along dolomite, and dolomitic shale in the western part of the major anticlinal axes and faults or fractures where secondary basin. The sandy and silty beds in the Glenwood thin to the dolomitization has taken place. east, and most of the formation is greenish-gray pyritic shale The Trenton Group, as well as the underlying Black River in central Michigan. Group, strata are important oil and gas zones in Michigan. The Glenwood Shale appears to be a transitional bed The largest field discovered to date in the basin is the between the St. Peter Sandstone and the Black River Albion-Scipio field, which extends for 35 miles in a limestone. northwest-southeast direction across parts of Hillsdale, Jackson and Calhoun counties. This trend is comprised of Practical correlations of the Black River Group have been several narrow, linear oil fields located on or along a established by gamma ray logs throughout the basin. The probable deep-seated fault or fracture zone. Along the "Black River Shale" marker bed near the top of the group fractures, the Trenton and Black River rock has been (see Plate 48) can be used in some cases to locate the top of dolomitized, and it is from these dolomitized fractures that the Group successfully. The shale marker can be followed oil is localized (see Ells, 1962). Production from the field is over a large portion of Michigan, but in the northern area it in excess of 100 million barrels of oil and nearly 175,000,000 cannot be traced. The top of the Black River Group in the Mcf of gas (Ells, 1978). Both the Trenton and Black River northern area is determined by correlating the lower part of rocks have great potential for additional production in the the Trenton and upper part of the Black River in other future. regions and tracing the gamma ray log characteristics into northern Michigan (see Plates 7 and 21). The correlation of the Trenton Group throughout Michigan is well established. The top of the Group is easily Two persistent marker beds in the Black River Group, distinguished by the sharp break on the log curves from the indicated by lines BR-1 and BR-2 (see Plate 48), are useful in highly radioactive Utica Shale above to the upper limestone correlation. Tracing these marker beds shows the thinning of the Trenton. The base of the Group is generally selected and thickening of the Black River in various areas and also beneath the last argillaceous or slightly higher radioactive helps to identify the Glenwood. The Glenwood member is portion of the Trenton (see Plates 33 and 60). generally much more radioactive than most of the Black

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 25 of 36 River; but in certain parts of the basin (see Plates 14, 21 and the east. The formation usually is well cemented by Ik) this is not true. dolomite and has low porosity and permeability. Porosity zones in the Black River occur in some areas, and The Oneota Dolomite is the oldest Ordovician formation in one such zone is shown on Plate 60. At the southern end of the subsurface. It is by far the thickest formation of the the Albion-Scipio Trend this porosity zone is most often Prairie du Chien Group. As much as 600 feet of Oneota has called the Van Wert Zone. been reported in western Michigan, but 250 to 300 feet of beds is a more common occurrence. According to Syrjamaki St. Peter Sandstone (1977) the Oneota reflects a gradual thickening into the basin off the shelf area in Wisconsin with the depocenter The St. Peter Sandstone underlies the Black River Group located in west central Michigan. It thins toward the east except where it has been removed by erosion. It is and is absent in the southeastern portion of the basin. The composed predominantly of well-rounded, subspherical, unit in general terms is a light brown to light gray dolomite. coarse to fine grained quartz. Coarse grained sandstone is Chert is a common constituent, and some of the chert may generally found in the lower portion but the sand becomes be oolitic. Small amounts of silty dolomitic shale are also finer grained in the upper part. Wherever calcareous cement present in the Oneota in certain portions of the basin. is not present, the St. Peter is highly porous and permeable. According to Syrjamaki (1977), salient points substantiating The formation appears to have been deposited on an an unconformity at the top of the Prairie du Chien Group erosion surface at the top of the Prairie du Chien Group. In are: 1) high relief at the contact; 2) the common occurrence western Michigan the thickness of the St. Peter is variable. of the basal St. Peter which is composed of chert The sandstone may be 200 feet thick in one well, but may be and sandstone; 3) the St. Peter Sandstone is very thin or absent only a few miles away. The St. Peter usually thickest where the Prairie du Chien is thinnest, and thins to the east across the basin and is not present along the conversely; 4) the top of the St. Peter Sandstone does not eastern rim. reflect the relief at the top of the Prairie du Chien; and 5) the The St. Peter Sandstone is not well defined by gamma ray St. Peter sometimes un-conformably overlies the upper log curves and therefore has not been correlated in this Cambrian formations. This unconformity is often referred study. to as the Post-Knox Unconformity and it is a widespread stratigraphic break not only throughout the eastern , but also over many other parts of the world. Prairie du Chien Group Selecting the top of the Prairie du Chien Group on gamma Prairie du Chien rocks of Early Ordovician age underlie ray logs is difficult because of the presence or absence of the Middle Ordovician sediments. St. Peter and the unconformity below the Glenwood. Since In the subsurface the group is divided, in descending order, the St. Peter has not been identified on the logs in these into Shakopee Dolomite, New Richmond Sandstone, and cross-sections, the top of the Prairie du Chien Group is Oneota Dolomite. These formations are usually not well- arbitrarily placed at the base of the Glenwood. defined on electric logs, and in this investigation no attempt has been made to delineate them. Apparently the rocks of the Prairie du Chien Group are thickest in the western and Cambrian System central portion of the basin and have been removed by erosion in the east. In much of eastern and southeastern The Cambrian System occurs throughout the Michigan Michigan, all of the Prairie du Chien has been eroded away Basin. It is composed of the Trempealeau Formation and and Middle Ordovician rocks overlie the Cambrian. the . The Trempealeau, shown on Chart 1, is divided into three members which are, in descending The Shakopee Dolomite is the upper formation of the order, the , the Lodi, and the St. Lawrence. Prairie du Chien Group and is thickest in western Michigan, The Munising is made up of four members, the Franconia where it may be as much as 225 feet thick. It consists Sandstone, Dresbach Sandstone, Eau Claire, and Mt. Simon predominantly of medium brown to medium gray dolomite Sandstone. According to Chart 1, the basal formation of the and sandy dolomite, with local occurrences of dolomitic Cambrian is the . However, Fowler shale. Some chert may also be present in the Shakopee. and Kuenzi (1978) have indicated that the Jacobsville may The New Richmond Sandstone, underlying the Shakopee, is be late Keweenawan. a relatively thin unit in Michigan. In Illinois as much as 200 Most geologists working with electric log correlations in feet of New Richmond Sandstone has been reported, while Michigan do not subdivide the Trempealeau into individual in western Michigan the formation is only 5 to 20 feet thick. members. The Trempealeau consists predominantly of It is composed of quartz sand and silt and is coarsest along dolomite which may be sandy in certain areas. It also the western portion of the basin, becoming finer grained to contains a minor amount of shaly dolomite and dolomitic

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 26 of 36 shale. The Jordan Sandstone, where present and of the Mt. Simon, as well as some of the other Cambrian recognizable, may range from a sandy dolomite in the units, is usability in industry. Some industries need to southern portion of Michigan to a quartz sandstone with dispose of liquid waste, and the depth, porosity, and well-rounded and frosted grains. The Lodi is usually a white permeability of Cambrian units are acceptable for this to buff dolomite, sometimes slightly sandy. Purple dolomite purpose. No commercial amounts of hydrocarbons have may also be found in the basal part of the Lodi in some been found to date in Cambrian rocks in Michigan. But areas of the State. The basal member of the Trempealeau, Cambrian tests in Michigan have been rare, and perhaps the St. Lawrence, is basically a dark gray dolomitic shale and future exploration will find economically recoverable dolomite, with some gray sandy glauconitic dolomite in the hydrocarbons. basal portion. The Trempealeau is more than 500 feet thick Correlation of Cambrian formations and members in this in certain portions of southeastern Michigan. study is offered as a guide for future efforts to delineate The Munising is the lowermost formation of the Cambrian these units more accurately than is presently possible. More System in the basin. It is predominantly sandstone with research is needed to determine the lithology and its abundant glauconitic in the three upper members, but little application to gamma ray logs so that the units may be or no glauconite is found in the basal Mt. Simon member. defined with a greater degree of accuracy. All four members, shown on Chart 1, are usually indicated in The writer believes that the Cambrian units are defined fairly electric log correlations. The members, in some areas of the accurately in the sections for southwestern Michigan (see basin, have sufficient diagnostic gamma ray characteristics to Plates 43, 49 and 55). These correlations were guided by permit correlations with an acceptable degree of accuracy. correlations described by Ells (1967b) and by work The upper member of the Munising in the subsurface is the conducted by Catacosinos (1973). Some Michigan wells Franconia Sandstone. According to Catacosinos (1973) it is were correlated with a well in Illinois in the study by Ells. As defined as a highly variable zone of dolomitic sandstone, shown on Plate 49 in the Upjohn No. 3 well, the top of the shale and sandy dolomite and is generally quite glauconitic. Trempealeau is placed below the last high-radioactive zone From areas where it can be identified, it appears to thicken of the Prairie du Chien and above the somewhat cleaner and westward to about 95 feet in Ottawa County. less-radioactive sand of the Trempealeau. The top of the Munising Formation, Franconia member, is then selected as Beneath the Franconia Sandstone is the Dresbach the first group of strata that shows higher radioactivity than Sandstone, which was called Galesville by Catacosinos the Trempealeau (see Plate 49, the BD No. 153 well). The (1973). The Dresbach has been described as a light gray, Franconia includes all strata which maintain a higher medium grained, subangular sandstone. The upper portion radioactivity than the surrounding beds. Selection of the contains some glauconitic, dolomitic sandstone, but Dresbach member is generally based on its characteristic throughout the remainder of the unit this glauconitic and lower radioactivity than the surrounding formations; so the dolomitic sandstone is absent. The Dresbach appears to be top is positioned at the base of the consistently higher- thickest in the southwestern corner of the State and thins radioactive Franconia member. The Eau Claire member, eastward. Catacosinos (1973) reported that the Dresbach is shown on Plates 43, 49 and 55, is much more radioactive not present in the area around Detroit. than the Dresbach and can usually be identified in the The Eau Claire, the next unit encountered, was named for southwestern quadrant of the State. The base of the Eau exposures at the mouth of the Eau Claire River in Eau Claire is chosen at the point below the last highly radioactive Claire County, Wisconsin. Cohee (I945a) described it as beds of the Eau Claire and at the top of the transitional, sandstone, shale, and dolomite that is sandy and shaly in interbedded high- and low-radioactive zone. The base of the southeastern Michigan. The dolomite beds may be variously Mt. Simon is chosen at the top of the first Precambrian colored within the unit and glauconite is sometimes locally strata, which are generally identified by a more highly abundant. The Eau Claire is thickest around Calhoun and radioactive gamma ray response (see Plate 49). Kalamazoo counties, and Catacosinos (1973) believes that In other parts of the State, correlations are considerably this member is confined to the lowest one-third of the State. more difficult because relatively few wells have penetrated Some variance of opinion exists as to where to establish the the Cambrian section and the wells are farther apart. In the contact between the Eau Claire and Mt. Simon Sandstone. southeastern quadrant of the State, considerable erosion of The Mt. Simon Sandstone is the lowermost member of the Cambrian rocks has occurred, as shown on Plate 75. In St. Munising Formation. It is composed predominantly of Clair County, southeastern Michigan, the Cambrian has been medium to coarse grained sandstone with subangular to excessively eroded and only portions of the system remain rounded grains. It is dominantly silica-cemented and above the Precambrian basement. generally light colored near the top, but may become more In northern Michigan even fewer Cambrian tests have been pink near the base, reflecting an increase in hematite and drilled than in southern Michigan. Comparisons of wells feldspar content. It is thickest in the western portion of the from the northern and the southern parts of the State are State, and thins gradually to the east. An important feature Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 27 of 36 nearly impossible because of facies changes in the sediments feet of red beds beneath the Mt. Simon sandstone are and lack of well control. Some of these changes and the believed to be of late Keweenawan age. The only other well problems involved can be seen on Plate 8. For instance, in that has encountered red beds at depth in any significant the State-Foster No. 1 well, located in Ogemaw County, quantity is the State-Beaver Island No. 1, shown on Plate 22. much of the Cambrian indicates a high radioactive response, It is possible that these beds may be stratigraphically and making correlation with some of the wells in southern genetically related to the red beds in the McClure deep test. Michigan difficult. An attempt was made, however, to correlate the Cambrian units from other wells to the State- Foster No. 1. Literature Cited

The deepest well drilled to date in the Southern Peninsula, Ailing, H. L. and L. I. Briggs, 1961, Stratigraphy of Upper Silurian the McClure Oil Company -Sparks, Eckelbarger-Whightsil Cayugan Evaporites, American Association of Petroleum No. 1-8 in Gratiot County, displays a unique Cambrian Geologists Bulletin, 45, no. 4, p. 515-547. section. All of the Cambrian formations are thicker and Asseez, L. 0., 1967, Stratigraphy and Paleogeography of the Lower show different radioactive responses than the same Mississipian Sediments of the Michigan Basin, Dissertation, formations in southwestern Michigan. Michigan State University. All of the sections dealing with the Cambrian are more Baltrusaitis, E. J., 1974, Middle Devonian Bentonite in Michigan, American Association of Petroleum Geologists Bulletin, v. 58. difficult to correlate because the units are thicker and less well-defined. The section for the McClure well has been Bishop, M. S., 1940, Isopachous Studies of Ellsworth to Traverse separated into two parts, the first extending from the Limestone Section of Southwestern Michigan, American Association of Petroleum Geologists Bulletin, v. 2k, no. 12, p. Glenwood to the middle of the Eau Claire member, and the 2150-2162. remainder showing the section from the Eau Claire to the red beds, which show higher radioactivity and are thought to Bishop, M. S., 1951, Thickness and Lithology of Upper Devonian and Rocks in Michigan, United States be Precambrian in age. The latter red beds are shown in Geological Survey, Oil and Gas Investigation, Chart OC 41. more detail on Plate 83. Bishop, M. S., et al., 1950, Coal Resources of Michigan, United States Geological Survey Circular 77. Precambrian Bishop, M. S., and L. B. Underwood, 1944, Maps and Sections of the Berea Sandstone of Eastern Michigan, United States Only 30 Precambrian basement tests have been drilled in the Geological Survey, Oil and Gas Investigation, Preliminary Southern Peninsula of Michigan through 1978. The paucity Map no. 17. of direct geologic information about the basement rocks in Bishop, M. S., and L. B. Underwood, 1945, Lithology and the subsurface has encouraged the use of geophysical Thickness of the Dundee Formation and the Rogers City methods, primarily gravity and magnetic, to determine the Limestone in the Michigan Basin, United States Geological Survey, Oil and Gas Investigation, Preliminary Map no. 38. nature of these rocks (Hinze and Merritt, 19&9). Gravity and magnetic data suggest that mafic rocks are widespread Carman, J. E., 1936, Sylvania Sandstone of Northwestern Ohio, Geological Society of America Bulletin, v. 47, p. 253-265- throughout the basement of the Michigan Basin, although most of the basement drill holes have encountered granitic Catacosinos, P. A., 1973, Cambrian Lithostratigraphy of the rocks. Michigan Basin, American Association of Petroleum Geologists Bulletin, v. 57, no. 12, p. 2404-2418. According to Hinze and Merritt (1969), four major Chung, P. K., 1973, Mississippian Coldwater Formation of the provinces are represented in the Southern Peninsula. These Michigan Basin, Dissertation, Michigan State University. are: l) the Grenvilie province in southeastern Michigan, Cohee, G. V., 1945a, Sections and Maps of Lower Ordovician and which is 0,8 to 1.0 billion years old; 2) the Central province Cambrian Rocks in the Michigan Basin, Michigan and in southwestern and southcentral Michigan, which is 1.2 to Adjoining Areas, United States Geological Survey, Oil and 1.5 billion years; 3) the Penokean province, 1.6 to 1.8 billion Gas Investigation, Preliminary Chart no. 9 years old, underlying the northern portion of the Southern Cohee, G. V., 1945b, Geology and Oil and Gas Possibilities of Peninsula; and 4) a rift zone transecting the Peninsula from Trenton and Black River Limestones of the Michigan Basin, northwest to southeast, which is 1.1 ±0.1 billion years old. Michigan and Adjacent Areas, United States Geological The rift zone is connected with the source of the Mid- Survey, Oil and Gas Investigation, Preliminary Chart no. 11. Continent gravity high through the Lake Superior Basin, and Cohee, G. V., 1947, Lithology and Thickness of the Traverse some geologists believe that it played a dominant role in the Group in the Michigan Basin, United States Geological development of the Michigan Basin. Survey, Oil and Gas Investigation, Preliminary Chart no. 28. Cohee, G. V., 1948, Thickness and Lithology of Upper The McClure Oil Company deep test in Gratiot County Ordovician, and Lower and Middle Silurian Rocks in the penetrated further into Precambrian sediments than any Michigan Basin, United States Geological Survey, Oil and Gas other well drilled in the Southern Peninsula. The 5,000+ Investigation, Preliminary Chart no. 33

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 28 of 36 DeWitt, W. Jr., I960, Geology of the Michigan Basin with Landes, K. K., G. M. Ehlers, and G. M. Stanley, 1945, Geology of Reference to Subsurface Disposal of Radioactive Wastes, Mackinac Straits Region and Subsurface Geology of Northern United States Geological Survey, Trace Elements Southern Peninsula, Michigan Department of Conservation, Investigations Report 771., Age of Bedford Shale, Berea Geological Survey, Publication 44, Geological ser. 37. Sandstone, and Sunbury Shale in the Appalachian and Landes, K. K., 1945a, The Salina and Bass Islands Rocks in the Michigan Basins, , Ohio and Michigan, United Michigan Basin, United States Geological Survey, Oil and Gas States Geological Survey Bulletin, 1294-G, p. 61-611. Investigation, Preliminary Map no. 40. Dorr, J. A., and D. F. Eschman, 1971, Geology of Michigan, Ann Landes, K. K., 1945b, Geology and Oil and Gas Possibilities of Arbor, Michigan: University of Michigan Press. Sylvania and Bois Blanc Formations of Michigan, United Ells, G. D., 1958, Notes on the Devonian-Silurian in the States Geological Survey, Oil and Gas Investigation, Subsurface of Southwest Michigan, Michigan Department of Preliminary Map no. 28. Conservation, Geological Survey, Progress Report no. 18. Landes, K. K., 1951, Detroit River Group in the Michigan Basin, Ells, G. D, 1962, Structures Associated with the Albion-Scipio Oil United States Geological Survey Circular 133- Field Trend, Michigan Department of Natural Resources, Majedi, M., 1969, Subsurface Study of the Detroit River Group of Geological Survey, Open File Report MGSD OFR AST. Southeast Michigan, Master of Science Thesis, Michigan State Ells, G. D, 1967a, Michigan's Silurian Oil and Gas Pools, Michigan University. Department of Natural Resources, Geological Survey, Report Matthews, R. and G. C. Egleson, 1974, Origin and Implications of of Investigation 2. a Mid-Basin Potash Fades in the Salina Salt of Michigan, The Ells, G. D, 1967b, Correlation of Cambro-Ordovician Rocks in Northern Ohio Geological Society, Fourth Symposium on Michigan, In; Correlation Problems of the Cambrian and Salt, v. 1, p. 15-33- Ordovician Outcrop Areas, Northern Peninsula of Michigan, Mesolella, K. J., et al., 1974, Cyclic Deposition of Silurian Michigan Basin Geological Society Annual Field Excursion Carbonates and Evaporites in Michigan, American 1967. Association of Petroleum Geologists Bulletin, v. 58, no. 1, p. Ells, G. D, 1978, Michigan's Oil and Gas Fields, 1977, Annual 34-62. Statistical Summary 28, Michigan Department of Natural Mesolella, K. J., and B. W. Weaver, 1975, Resources, Geological Survey. What is the Effect of Salt Collapse Structures on Finds in Ells, G. D, 1979, Stratigraphic Cross Sections Extending from Michigan Basin Arena, The Oil and Gas Journal, p. 166-168. Devonian Antrim Shale to Mississippian Sunburn/ Shale in Monnett, V. B., 1948, Mississippian Marshall Formation of the Michigan Basin, Michigan Department of Natural Michigan, American Association of Petroleum Geologists Resources, Geological Survey, Report of Investigation 22. Bulletin, v. 32, no. 4, p. 629-688. Evans, C. S., 1950, Underground Hunting in the Silurian of Moser, F. B., 1964, The Michigan Formation, Master of Science Southwestern Ontario, Proceedings of the Geological Thesis, University of Michigan. Association of , v. 3 Newcome, R. B., 1933, Oil and Gas Fields of Michigan, Michigan Fisher, J. H., et al., 1969, Stratigraphic Cross-Sections of the Department of Conservation, Geological Survey Publication Michigan Basin, Michigan Basin Geological Society 38, Geological series 32. Publication. Nurmi, R. D., 1972, Upper Ordovician Fowler, J. H. and W. D. Kuenzi, 1978, Keweenawan Turbidites in Michigan (Deep Borehole Red Beds): A Foundered Basin Stratigraphy of the Southern Peninsula of Michigan, Master of Sequence Developed During Evolution of a Protoceanic Rift Science Thesis, Michigan State University. System, Journal of Geophysical Research, v. 83, no. 12. Rawlins, E. L. and M. A. Schellhardt, 1936, Extent and Availability Gardner, W. C., 1974, Middle Devonian Stratigraphy and of Natural Gas Reserves in Michigan "Stray" Sandstone Depositional Environments in the Michigan Basin, Michigan Horizon of Central Michigan, United States Bureau of Mines Basin Geological Society, Special Paper no. 1. Report of Investigation 3313- Ha1e, L., 1941, Study of Sediments and Stratigraphy of the Lower Shaffer, B. L., 1969, Palynology of the Michigan "Red Beds", Mississippian in Western Michigan, American Association of Dissertation, Michigan State University. Petroleum Geologists Bulletin, v. 25, p. 713-723. Shelden, F. D., 1963, Transgressive Marginal Lithotopes in Hautau, G., 1952, The Richfield Challenge, Michigan Department Niagaran (Silurian) Northern Michigan Basin, American of Conservation, Geological Survey, Progress Report no. 15. Association of Petroleum Geologists Bulletin, v. 47, no. 1, p. 129-149. Hinze, J. W., and D. W. Merritt, 1969, Basement Rocks of the Southern Peninsula of Michigan, In; Studies of the Sherzer, W. H. and A. W. Grabau, 1909, The Sylvania Sandstone, Precambrian of the Michigan Basin, Michigan Basin its Distribution, Nature and Origin, Michigan Geological Geological Society Annual Field Excursion, 1969. Survey Publication 2, Chapter 3, p. 61-86. Kalliokoski, J. and E. J. Welch, 1976, Magnitude and Quality of Sorensen, H. 0., and R. T. Segall, 1974, Natural Brines of the Michigan's Coal Reserves, United States Bureau of Mines, Detroit River Group, Michigan Basin, The Northern Ohio Open File Report 102-76. Geological Society, Fourth Symposium on Salt, v. 1, p. 91-99- Knapp, T. S., 1947, A Theory of Rogers City and Dundee Syrjamaki, R. M., 1977, The Prairie du Chien Group of the Relationships in Central Michigan, unpublished Report. Michigan Basin, Master of Science Thesis, Michigan State University. Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 29 of 36 Ulteig, J. R., 1963, Upper Niagaran and Cayugan Stratigraphy in the Subsurface of Northeastern Ohio, In; Stratigraphy of Silurian Rocks in Western Ohio, Michigan Basin Geological Society Annual Field Excursion, 1963.

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 30 of 36 Plate CS From To Systems shown Plate A-D Gratiot to Leelanau Upper and Illustrations 28 Middle Ordovician Plate A-E Gratiot to Mason Pennsylvanian and Figure 1. General Bedrock Geology Map of Michigan. 29 Mississippian Plate A-E Gratiot to Mason Lower Mississippian to Chart 1. Stratigraphic Succession in Michigan, Chart 1, 30 Middle Devonian 1964. Plate A-E Gratiot to Mason Middle Devonian to 31 Upper Silurian Plates not included available in print only Plate A-E Gratiot to Mason Middle and Plate CS From To Systems shown 32 Lower Silurian Plate Index map showing lines Plate A-E Gratiot to Mason Upper and 1 of cross-section 33 Middle Ordovician Plate A-A1 Gratiot to Alpena Pennsylvanian and Plate A-F Gratiot to Oceana Pennsylvanian and 2 Mississippian 34 Mississippian Plate A-A1 Gratiot to Alpena Lower Mississippian to Plate A-F Gratiot to Oceana Lower Mississippian to 3 Middle Devonian 35 Middle Devonian Plate A-A1 Gratiot to Alpena Middle Devonian Plate A-F Gratiot to Oceana Middle Devonian to 4 36 Upper Silurian Plate A-A1 Gratiot to Alpena Middle Devonian to Plate A-F Gratiot to Oceana Middle and 5 Upper Silurian 37 Lower Silurian Plate A-A1 Gratiot to Alpena Middle and Plate A-G Gratiot to Ottawa Pennsylvanian and 6 Lower Silurian 38 Mississippian Plate A-A1 Gratiot to Alpena Upper and Plate A-G Gratiot to Ottawa Upper and 7 Middle Ordovician 39 Middle Devonian Plate A-A1 Gratiot to Alpena Lower Ordovician to Plate A-G Gratiot to Ottawa Middle Devonian to 8 Precambrian 40 Upper Silurian Plate A-B Gratiot to Emmet Pennsylvanian and Plate A-G Gratiot to Ottawa Middle and 9 Mississippian 41 Lower Silurian Plate A-B Gratiot to Emmet Lower Mississippian to Plate A-G Gratiot to Ottawa Upper and 10 Middle Devonian 42 Middle Ordovician Plate A-B Gratiot to Emmet Middle Devonian Plate A-G Gratiot to Ottawa Lower Ordovician to 11 43 Precambrian Plate A-B Gratiot to Emmet Middle Devonian to Plate A-H Gratiot to Berrien Pennsylvanian and 12 Upper Silurian 44 Mississippian Plate A-B Gratiot to Emmet Middle and Plate A-H Gratiot to Berrien Lower Mississippian to 13 Lower Silurian 45 Middle Devonian Plate A-B Gratiot to Emmet Upper and Plate A-H Gratiot to Berrien Middle Devonian to 14 Middle Ordovician 46 Upper Silurian Plate A-B Gratiot to Emmet Lower Ordovician to Plate A-H Gratiot to Berrien Middle and 15 Precambrian 47 Lower Silurian Plate A-C Gratiot to Charlevoix Pennsylvanian and Plate A-H Gratiot to Berrien Upper and 16 Mississippian 48 Middle Ordovician Plate A-C Gratiot to Charlevoix Lower Mississippian to Plate A-H Gratiot to Berrien Lower Ordovician to 17 Middle Devonian 49 Precambrian Plate A-C Gratiot to Charlevoix Middle Devonian Plate A- Gratiot to Cass Pennsylvanian and 18 50 Mississippian Plate A-C Gratiot to Charlevoix Middle Devonian to Plate A- Gratiot to Cass Upper and 19 Upper Silurian 51 Middle Devonian Plate A-C Gratiot to Charlevoix Middle and Plate A- Gratiot to Cass Middle Devonian to 20 Lower Silurian 52 Upper Silurian Plate A-C Gratiot to Charlevoix Upper and Plate A- Gratiot to Cass Middle and 21 Middle Ordovician 53 Lower Silurian Plate A-C Gratiot to Charlevoix Lower Ordovician to Plate A- Gratiot to Cass Upper and 22 Precambrian 54 Middle Ordovician Plate A-D Gratiot to Leelanau Pennsylvanian and Plate A- Gratiot to Cass Lower Ordovician to 23 Mississippian 55 Precambrian Plate A-D Gratiot to Leelanau Lower Mississippian to Plate A-J Gratiot to Hillsdale Pennsylvanian and 24 Middle Devonian 56 Mississippian Plate A-D Gratiot to Leelanau Middle Devonian Plate A-J Gratiot to Hillsdale Upper and 25 57 Middle Devonian Plate A-D Gratiot to Leelanau Middle Devonian to Plate A-J Gratiot to Hillsdale Middle Devonian to 26 Upper Silurian 58 Upper Silurian Plate A-D Gratiot to Leelanau Middle and Plate A-J Gratiot to Hillsdale Middle and 27 Lower Silurian 59 Lower Silurian

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 31 of 36 Plate CS From To Systems shown Plate CS From To Systems shown Plate A-J Gratiot to Hillsdale Upper and Plate A-N Gratiot to Sanilac Pennsylvanian and 60 Middle Ordovician 76 Mississippian Plate A-K Gratiot to Monroe Pennsylvanian and Plate A-N Gratiot to Sanilac Lower Mississippian to 61 Mississippian 77- Middle Ordovician Plate A-K Gratiot to Monroe Upper and Plate A-N Gratiot to Sanilac Middle Devonian 62 Middle Devonian 78 Plate A-K Gratiot to Monroe Middle Devonian to Plate A-N Gratiot to Sanilac Middle Devonian to 63 Upper Silurian 79 Upper Silurian Plate A-K Gratiot to Monroe Middle and Plate A-N Gratiot to Sanilac Middle and 64 Lower Silurian 80 Lower Silurian Plate A-K Gratiot to Monroe Upper and Plate A-N Gratiot to Sanilac Upper and 65 Middle Ordovician 81 Middle Ordovician Plate A-L Gratiot to Wayne Upper and Plate A-N Gratiot to Sanilac Lower Ordovician to 66 Middle Devonian 82 Precambrian Plate A-L Gratiot to Wayne Middle Devonian to Plate A-N Gratiot to Sanilac Lower Ordovician to 67 Upper Silurian 83 Precambrian Plate A-L Gratiot to Wayne Middle and Plate A-0 Gratiot to Huron Pennsylvanian and 68 Lower Silurian 84 Mississippian Plate A-L Gratiot to Wayne Upper and Plate A-0 Gratiot to Huron Lower Mississippian to 69 Middle Ordovician 85 Middle Devonian Plate A-M Gratiot to St. Clair Pennsylvanian and Plate A-0 Gratiot to Huron Middle Devonian 70 Mississippian 86 Plate A-M Gratiot to St. Clair Upper and Plate A-0 Gratiot to Huron Middle Devonian to 71 Middle Devonian 87 Upper Silurian Plate A-M Gratiot to St. Clair Middle Devonian to Plate A-0 Gratiot to Huron Middle and 72 Upper Silurian 88 Lower Silurian Plate A-M Gratiot to St. Clair Middle and Plate A-0 Gratiot to Huron Upper and 73 Lower Silurian 89- Middle Ordovician Plate A-M Gratiot to St. Clair Upper and 74 Middle Ordovician Plate A-M Gratiot to St. Clair Lower Ordovician to 75- Precambrian

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 32 of 36 Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 33 of 36 Appendix 1 – Well Records Used to Create Cross-Sections

X Well Name PN Sec T R Township County A McClure Oil Co. / Sparks, Eckel barger, S Whightsil #1-8 29739 8 10N 2W North Star Gratiot A Pure Oil Co. / Merton Emery #1 23849 21 13N 1W Porter Midland A Tribal Oil Co. / John Kucharski #1-32 29135 32 17N 3E Mt. Forest Bay A Charles J. Moskowitz / Minnie Biener #1 28907 13 20N 4E Clayton Arenac A Brazos-Sun-Superior / State Foster #1 25099 28 24N 2E Foster Ogemaw A Natural Gasoline Corp. / State-Hawes #1 24359 20 27N 8E Hawes Alcona A Amoco Production Co. / Garland #1 28546 16 28N 1E Greenwood Oscoda A Getty Oil Co. / Charles A. Cain #1-21 28866 21 31N 4E Hillman Montmorency A Shell Oil Co. / Shel don-State-Wel 1 i ngton #1-34 29571 34 32N 5E Wellington Alpena A Shell Oil Co. / Taratuta #1-13 29372 13 33N 5E Metz Presque Isle A Panhandle Eastern Pipe Line Co. / Ford Motor Co. #1-5 25690 5 31N 9E Alpena Alpena B McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot B Pure Oil Co. / Merton Emery #1 23849 21 13N 1W Porter Midland B Tribal Oil Co. / Roy Nettleton #1-26 29066 26 19N 1W Gladwin Gladwin B Union Oil Co. of California / State-Beaver Creek #C-4 28110 21 25N 4W Beaver Creek Crawford B Union Oil Co. of California / State-Maple Forest #1-4 29602 4 28N 3W Maple Forest Crawford B Woody's Oil & Gas, Inc. / Saddler Unit #1-35 30349 35 31N 2W Dover Otsego B Shell Oil Co. / State-Nunda #1-3 27976 3 33N 1W Nunda Cheboygan B Pan American Petroleum Corp. / D. E. Draysey #1 27199 29 35N 2E North All is Presque Isle B Northern Mich. Explor. Co. & Tribal Oil Co. / State-Waverly #1-24 30682 24 35N 1W Waverly Cheboygan B Atlantic Inland Oil Corp. / E. G. White & T. R. Burns #1 28212 35 37N 4W McKinley Emmet C McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot C Pure Oil Co. / Merton Emery #1 23849 21 13N 1W Porter Midland C Thomas H. Mall / Axel Johnson #1 31106 36 17N 4W Grant Clare C Sun Oil Co. / Mary Yake #1 22435 21 20N 4W Frost Clare C Sun Oil Co. / Enterprise Unit Tract #11-E3 30522 11 23N 5W Enterprise Missaukee C Miller Brothers / Clara Gibbons #1-26 29691 26 27N 6W Excelsior Kalkaska C C. J. Simpson / Lake Horicon Corp. #1 25873 2 29N 4W Hayes Otsego C Forrest H. Lindsay / Lawrence Wolgamott #1 22639 19 32N 8W Banks Antrim C Paul G. Benedum S MGU Dev. Co. / James E. Clark et ux. #1 29119 14 34N 7W Hayes Charlevoix C McClure Oil Co. / State-Beaver Island #1 23435 27 38N 10W Peaine Charlevoix D McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot D McClure Oil Co. / Terry Childs et al. #1-22 29916 22 13N 4W Lincoln Isabella D Woods Oil Co. / Merrill Palmer School #1 27210 8 16N 6W Coldwater Isabella D Sun Oil Co. / Victor E. Lindberg #1 23216 19 20N 10W Burdell Osceola D Northern Mich. Explor. Co., Tribal, S Miller Bros. / St.-Spr ingville #1-31 29037 31 23N 12W Springville Wexford D C. J. Simpson / Robert & Cecelia Northrup et al. #1 24557 8 24N 13W Cleon Manistee D Shell Oil Co. / Henry #1-4 29258 4 25N 11W Mayfield Grand Traverse D Miller Brothers / Russell Lyons #3~32 28919 32 27N 10W East Bay Grand Traverse D Forrest H. Lindsay / Anne Kirt #1 22627 6 30N 11W Suttons Bay Leelanau

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 34 of 36 X Well Name PN Sec T R Township County E McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot E McClure Oil Co. / Betham-Clark Unit #1-26 30027 26 10N 7W Sidney Montcalm E Gene Miller, Inc. / C. F. Seaman #1 22918 15 HN 13W Ashland Newaygo E Thunder Hollow Oil & Gas Co. / Walter & Rosilea Thompson #1 26662 20 15N 14W Beaver Newaygo E Sun Oil Co. / Jacobson Unit #3 25053 14 18N 7W Amber Mason E Miller Brothers / Gore, Zak, Coerper #1-11 29370 11 20N 16W Freesoil Mason F McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot F McClure Oil Co. / Betham-Clark Unit #1-26 30027 26 10N 7W Sidney Montcalm F Gene Miller, Inc. / C. F. Seaman #1 22918 15 HN 13W Ashland Newaygo F Hibbard Oil Corp. / Mary & Antoinette Rutkowski #1 28931 8 12N 17W Montague Muskegon F Tribal Oil Co. & Chapman Drilling Co. / John Garcia Unit #1 28203 20 14N 17W Shelby Oceana F MGU Dev. Co. / F. Bailly Unit #1-27 30169 27 15N 18W Golden Oceana G McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot G Ambassador Oil Corp. / Samuel Ten-Cate #1 24619 34 7N 8W Keene Ionia G Ambassador Oil Corp. / John Ten Have #1 24826 6 8N 9W Grattan Kent G Beacon Resources Corp. / B. E. Goss #1 27296 35 9N 10W Courtland Kent G McClure, M.I.O., & Gordon / Vormittag #1 22852 9 8N 14W Polkton Ottawa G Parke-Davis & Co. / Brine Disposal #3 { 21 139 00114 80 00 } 20 5N 15W Holland Ottawa H McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot H McClure Oil Co. / Wildman #1 23574 15 5N 7W Odessa Ionia H McClure Oil Co. / Schaibly #1 23572 20 4N 7W Woodland Barry H Battle Creek Gas Co. / BD #2-153 { 21 015 00153 80 00 } 14 1N 8W Johnstown Barry H Continental Oil Co. / Simpson #1 23685 10 2N 12W Watson Allegan H Upjohn Co. / Upjohn #3 { 21 077 00137 70 00 } 14 3S 11W Portage Kalamazoo H Turtle Drilling Co. / Kern #1 23524 34 4S 14W Decatur Van Buren H Security Oil & Gas Co. / Thalmann #1 26112 10 6S 17W Berrien Berrien I McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot I McClure Oil Co. / Fox #1 27811 6 7N 1W Ovid Clinton I Hibbard Oil Corp. / R. A. Seibly #1 28929 33 2N 2W Aurelius Ingham I Mobil Oil Corp. / Gladys Kelly Unit #1 29117 24 2N 3W Eaton Rapids Eaton I M.I.O. Explor. Co. / Schneeberger-Murphy #1 28263 27 1N 5W Walton Eaton I Earl Midlam / Midlam #1 30468 13 1S 5W Lee Calhoun I Trenton Pet. & McClure Oil Co. / Bernloehr-Bole-Eitniear #1 22352 13 3S 8W Leroy Calhoun I Consumers Power Co. & Quintana Prod. Co. / Harvey Clark #1 29969 8 5S 8W Sherwood Branch I C. J. Simpson / Harold Walters #1 C. 24183 29 6S 9W Colon St. Joseph I A. Perry & Son / Wooden #1 23289 8 7S 14W Calvin Cass J McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot J McClure Oil Co. / Fox #1 27811 6 7N 1W Ovid Clinton J Hibbard Oil Corp. / R. A. Seibly #1 28929 33 2N 2W Aurelius Ingham J Mobil Oil Corp. / Gladys Kelly Unit #1 29117 24 2N 3W Eaton Rapids Eaton J McClure Oil Co. / Crawford #1 26481 4 1S 3W Springport Jackson J Texaco, Inc. / Stella Konkol #1 26541 15 2S 2W Sandstone Jackson J McClure Oil Co. / Harlan J. Bellis et al. #1 23013 17 4S 2W Hanover Jackson J Jenkins & Woodruff, Inc. / Edwin Houseknecht #1 24378 31 5S 2W Moscow Hillsdale J Texaco, Inc. / Percy Edmonds #1 26078 10 7S 2W Jefferson Hillsdale J Glynn Trolz & Assoc., Inc. / L. Laser #1 25158 15 8S 1W Wright Hillsdale Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 35 of 36

X Well Name PN Sec T R Township County K McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot K McClure Oil Co. / Fox #1 27811 6 7N 1W Ovid Clinton K Mobil Oil Corp. / Jelinek-Ferris Unit #1 27907 5 5N 2E Perry Shiawassee K Patrick Petroleum Corp. / R. Kleinschmidt #1 28752 17 2N 3E losco Livingston K William R. Albers / Hannawald #1 28620 6 1S 3E Lyndon Washtenaw K A. E. Rovsek / Irma Grau #1 27472 8 3S 4E Freedom Washtenaw K Leonard Oil Co. / George & Rose Schwocho #1 26856 17 4S 5E Saline Washtenaw K Bell & Marks & Good & Good Drilling / Thurlow Heath #G G-l 23531 4 5S 7E London Monroe K McClure Oil Co. / Stotz-Wi11 Jams #1 25062 10 7S 7E Ida Monroe L McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot L McClure Oil Co. / Fox #1 27811 6 7N 1W Ovid Cl inton L Mobil Oil Corp. / Jel inek-Ferri s Unit #1 27907 5 5N 2E Perry Shiawassee L Mobil Oil Corp. / Howard J. Messmore #1 27986 11 3N 5E Oceola Livingston L G. W. Strake / Manuel Lopez #1 24771 14 1N 6E Green Oak Livingston L A. E. Rovsek / Knudt Jorgensen #1 25714 26 2S 7E Superior Washtenaw L Consumers Power Co. / Consumers Power Co. #208 25538 22 1S 8E Plymouth Wayne L Panhandle Eastern Pipe Line Co. / Ford Motor Co. #1 25560 19 2S 11E City of Dearborn Wayne M McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot M McClure Oil Co. / Fox #1 27811 6 7N 1W Ovid Cl inton M Mobil Oil Corp. / Jel inek-Ferri s Unit #1 27907 5 5N 2E Perry Shiawassee M Mobil Oil Corp. / Howard J. Messmore #1 27986 11 3N 5E Oceola Livingston M Reef Petroleum Corp. / Investment Administrators, Inc. #1-26 31304 26 5N 10E Oxford Oakland M Cedco Drilling Co. / Richard Noonan et al. #1-14 31064 14 4N 11E Oakland Oakland M Consumers Power Co. / Joseph Halmich #3"! 26214 1 4N 13E Ray Macomb M Michigan Cons. Gas Co. / Osterland et al . #1-14 30376 14 3N 15E Ira St. Clair M Bernhardt Oil & Gas Co. / Paul & Arelane Puzzuoli #1 25780 17 2N 16E Clay St. Clair N McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot N Arch E. Turrentine / Robert Gage Coal Co. #1 23429 33 11N ?E Swan Creek Saginaw N Dugger-Herring & Wells / Hutchinson #1 24079 4 9N 8E Forest Genesee N Sunray Mid-Continent Oil Co. / H. G. Richardson #1 22534 18 6N 12E Almont Lapeer N Humble Oil & Refining Co. / Hoppinthal #1 25357 16 9N 15E Fremont Sanilac N McClure Oil Co. S Mich. Nat. Res. / Hewett & Shadd Unit #1-20 30974 20 12N 15E Bridgehampton San i lac O McClure Oil Co. / Sparks, Eckelbarger, & Whightsil #1-8 29739 8 10N 2W North Star Gratiot O Arch E. Turrentine / Robert Gage Coal Co. #1 23429 33 HN 3E Swan Creek Saginaw O Jack Mall / Leonard Elbers #1 22270 5 12N 6E Blumfield Saginaw O C. J. Simpson & Sun Oil Co. / B. & L. Sattelberg #1 23890 8 13N 9E Aimer Tuscola O C. J. Simpson / Novesta Township et al. #1 25609 16 13N 11E Novesta Tuscola O Mobil Oil Corp. / C. J. Volmering #1 29191 26 15N 15E Sherman Huron

Stratigraphic Cross-Sections of the Michigan Basin - RI 19 - page 36 of 36